Do you have interest in learning basic shell commands? Perhaps you’re new to Linux and want to become more familiar with the Terminal? Perhaps you’ve been using Linux for some time now, but never really got the hang of using the command line?
Codecademy has a nice beginner course on shell commands. You should definitely check this out. I consider myself an advanced user in this area and I still managed to learn a few things.
The course is free and should take less than an hour (I was done in 15 minutes and I took time to skim/read the lesson).