It might be best if you give us questions you're having trouble answering so we could point you to appropriate reading material. As you know there's a lot of information out there about Linux.
The linux documentation project
is a good start for any Linux newcomer. More specifically check out the Guides as there's a lot of useful in-depth information there.
On a more offline level, if you have a GNU/Linux distro setup to practice on you can
and then run man <some_command>
from the programs in the /usr/bin
folder. That is how I first learned about most the commands available in Linux which can be invaluable. For other paths which you can list out then echo the $PATH variable.