man is your friend
The command line is great. When you know how to use it properly, it can be the fastest way to achieve a task and it is endlessly extensible.
The problem is, commands and their syntax can be really tricky to remember. Sometimes you just can’t remember what a particular switch does, or what switch you need to perform a particular task. My common one until recently was always forgetting which way round you use ln (I’ve taught myself that it’s target, link name).
Thankfully, help is at hand, thanks to man.