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- [Instructor] Hi, and
welcome back to the course.

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In this video, we're going to look at

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what is a repository?

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This is important because Git is organised

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in a very specific way to
give you control and power.

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It's important to understand what Git is,

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because all Git commands
are used for one thing only.

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Git is a set of layers

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and each layer sort of has a function.

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The function is dependent on the layer

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but all you do with Git is you move files

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between these layers,
and the layers provide

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error control, redundancy,
and more things,

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so depending on the layer,
you get one thing or another.

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Let's look at these layers.

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The first layer is your filesystem.

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The filesystem is just your computer,

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so all the files that you've got.

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Git isn't this layer essentially,

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but this is the layer that
you've got before you use Git.

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Then, you can choose to initialise
Git in a specific folder.

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So you create a folder,
and you want this folder

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to be a Git repository, it
can initialise Git in it.

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Then, you've got this folder
with your Git repository in it,

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and so you create a file,
such as a Python file.

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These changes, that you've made
to this file you've created

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are not tracked by Git, by default,

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you have to tell Git that
you want to track this file.

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So what you do, is you tell
Git to include the files

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in the next snapshot.

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In this case, if it's only
one file, than you just add

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that file to the staging area.

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You add the file to the next commit.

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If you've incurred more
files, you can also add them

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to the staging area, and
eventually you end up

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with a staging area that has a few files,

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but changes are still not
tracked until you commit them;

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you create a snapshot of the files.

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So what you do, is you commit the files

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to the local repository,

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and this creates a snapshot of them.

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For example, if you create
a simple Flask application

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and you add it to the staging
area, and you commit it,

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that saves that file
in its current status.

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If you then add more code,
you will add it again

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to the staging area, and commit it again,

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and the changes between
version one and version two

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will be saved as a separate commit,

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and than as you do this more often,

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you may build up a history
of versions of your file,

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where each version has some more code.

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This means that you can go back
in time to a previous commit

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if you, for example, made a mistake,

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or you want to remove some code.

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Naturally, if your computer
blows up, you lose your files,

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because they are all in your computer,

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so the last thing to do,
is to host the snapshot,

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these commits, remotely,
so you can push these files

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to the cloud, and send them
to a Git service, like GitHub,

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or Bitbucket, these are
two separate services.

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A lot of people get confused
with GitHub and Git.

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Git is the thing that
allows you to move files

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between these layers and
allows you to commit and push.

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GitHub is essentially just a server

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that hosts your Git repository's

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so that you have a Git
repository in your computer,

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a local repository, and
also a remote repository;

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a repository that is hosted in GitHub.

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You are not limited to using
GitHub, so you could have

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a local repository, a
remote repository in GitHub,

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and a remote repository in Bitbucket,

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so you can have two remote
repositories for example.

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What's important to
remember is Git is the thing

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that allows you to do these things,

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GitHub is a server that hosts
your repository for you.

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So each layer has a
function, and it is optional

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to push your commits
to a remote repository,

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although again, if your
computer gets damaged,

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and you have your commits
in a remote repository,

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you can just download them again.

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So really it's helpful for redundancy

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and making sure you don't lose your data.

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And finally, the layers are all physical,

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it's not some sort of software magic.

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Git uses a folder called .git folder

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and whenever you make a new commit,

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that commit gets created there

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and it stores the new
snapshot and all those things,

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and when you push them to GitHub,

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all those snapshots get sent over

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and uploaded via your Internet
connection to GitHub servers.

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So there's no magic going on here.

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All Git is doing is
calculating the difference

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between your previous version
and your current changes

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and is storing those new
lines that you've added,

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that new code that you've added.

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And that's really all that Git is,

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is a way of storing snapshots,
and it is really helpful,

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because it means other
people can see your snapshots

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and than they can collaborate with you,

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and you can revert back
to previous snapshots,

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and you can host your snapshots
in the cloud for redundancy.

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So really, a great tool to
use, and I've not worked

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in a team that hasn't used
Git, so definitely something

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that you should learn.