GitHub dynamic statistics on markdown outputs (such as readme.md)

I have seen things that look like this:


in Github profiles and repositories. They are even clickable hyperlinks.

How does one make these, what are these called, and would there be a list out there of all the different possible stats you could show?

They are called badges so far I know:

seems possible to add badges to the readme:

Use the button at the bottom to copy your badge url or snippet, which can then be added to places like your GitHub readme files or other web pages.