You can use git differently, depending on your team size.
There are different branching strategies.
If you work alone:
It doesn't make so much sense to use a lot of branches. You can mainly use the master branch. It makes sense for larger changes to create branches, so you can continue working on the master branch, even though you are not finished with your work on the other branch.
If you work in a team:
You need multiple branches. The master branch is usually the one where the published version of your website or app is.
An example for a popular branching strategy for larger teams with continuous delivery:
https://nvie.com/posts/a-successful-git-branching-model/