Terminal command help

How can I learn my terminal commands? Also how do i get overall permission to amu file ,folder, hard drive, and live dostros file/folders? I would like to learn all the essentials that would help me determine what’s what in terminal as in know what to type instead of looking on google for “how to” and that would help me know what to type/look in/for especially more of taking permission of overall file or hard drive that I want to get into.