This is a blog about algebraic geometry and more specifically algebraic stacks and the stacks project. So let’s start with some basic information on the stacks project.
The stacks project is an open source text book on algebraic stacks and the algebraic geometry that is needed to define them. The current version of the complete book can always be found here.
How can you contribute? You can leave comments on this blog if you want to give feedback in an informal manner. Another simple way is to download the tex file and the pdf file of a chapter, and while you are reading correct any typos, or mathematical errors you see. At the end simply email the new tex file to email@example.com. You can take a look at the todo-list to see what needs to be done.