In this course, you will not learn everything there is to know about Git, but you will build a strong conceptual understanding of the technology, and afterward will be able to confidently dig deeper on any topic that interests you. This course assumes no previous knowledge of Git, but if you do have experience with it, you may find this course to be both useful and challenging. This is especially true if you currently "know just enough Git to be dangerous".
There are two paths in this course. Both rely heavily on hands-on labs. One path assumes that you have experience using a command line interface, and the other path uses the Sourcetree graphical client. If you are not experienced with a command line, we highly suggest that you go through the Sourcetree path. Eventually, you might want to go through both paths, so that you can decide which tool to use for specific tasks. Besides, repetition is good for learning :)
You can watch the videos and take the quizzes from your phone if you want, but the hands-on labs require you to have a Windows or Mac computer. If you use the command line path through the course, you can also use Linux.
This course uses Bitbucket (bitbucket.org) as the hosted provider for remote Git repositories. Bitbucket is free for teams of up to 5 people, including private repositories. However, most of the knowledge that you gain in this course applies to Git itself, and you can apply this knowledge to other hosted Git providers (such as GitHub).
This course tries to be as concise as possible. It will probably take you about 5-10 hours to go through one of the two paths, but your mileage may vary.