Hello!
This is the first time I've used a branch. They seem to be useful as a way of keeping what you're working on separate from what you had before. You can work on your branch then make a pull request and then merge things locally. I think this is different to how we usually work.
You can also use markup in your files.
And link to images with titles
Most important thing I learnt was that you can use emoji 
They're taking over the internet.
You can also fork other people's repositories and then they can choose whether or not to accept your changes.
Finally, if you're writing about code, you can comment it with 4 leading spaces:
<h1>The title</h1>
<p>And a paragraph</p>
👍