If you’re new to WordPress or software development, you might be wondering, “What the heck is Subversion?”
You’re not alone. It took me a while to figure it out. Simply put, Subversion (or SVN for short) is a version control system for software. It tracks all your changes and is especially helpful if you have multiple people working on the same project.
With the popularity of GitHub, Git has overtaken Subversion as the most popular version control system, but many open source projects are still using Subversion, notably WordPress.org.
So if you want to create themes or plugins for the WordPress.org repository or contribute updates to the core, you’ll need a basic understanding of Subversion. If you’re working with WordPress, this page has the basic instructions: How to Use Subversion