GitHub is a site that provides a platform for developing computer software code. We will use it for developing interactive textbooks. Not only does the site provide an easy way to upload, store, and download versions of the book, it always provides a straightforward method for keeping track of changes using the "git" software.
See our GitHub landing page.
R and R-studio have recently implemented a new package called "bookdown" that allows one to author books and technical documents using R's version of markdown. This package allows us to create .html, .pdf, and .EPUB versions of the same file.
We will use GitHub to host the code written in bookdown in addition to supporting files (e.g., data).
There are a lot of great resources for learning about Git for R users. Here is one.