
linuxcommand.org is a good resource for the command line specifically, and there are guides there for some other things like tmux.
Once you have a foundation of basic Linux skills, there are so many different directions you could go with the learning, it’s hard to write a singular guide. At that point it’s best to simply read up on different topics on the archwiki or similar resources.


A more accurate and detailed explanation is available by running
man hier