Git is a free and open-source version control system first introduced by Linus Torvalds. It is primarily used in software development to track and coordinate changes in files among multiple people. Understanding the system can be a bit overwhelming at first for complete beginners. But to jump-start you need to know just a couple of commands!
I like the tutorials by LearnCode.academy, which explains the basics of Git with examples in just two videos. The tutorials use GitHub as repository, instead of hosting the repository only on your local machine.
The first video covers how to initiate and clone GitHub repositories, how to commit and push changes, and how to pull changes made by others.
The second video talks about pull requests in the context of branching, merging and team workflow management.
Another handy resource to keep in your collection is the Git cheatsheet from GitHub. The cheatsheet contains all Git commands you would ever require.
BitBucket also has very good Git tutorials.