Markdown

Markdown is a simple language used for adding structure and styling to plain text. It's used a lot by developers for adding instructions and documentation to their code (especially README.md files). You will need to use Markdown for your projects on GitHub too.

Read this introduction to Markdown syntax.

See also: this markdown cheatsheet

How to check your Markdown is correct

In VSCode, while you are editing a Markdown file you can right-lick the file tab (at the top) and select "Open Preview". This will show you a rendered version of the markdown - similar to how it would show up in Github.

Alternatively: Here's a simple website markdown editor