> I have no idea what they mean

Emacs can "describe" anything contextually. Describe current mode, character at point, specific command, any variable, etc. With Wilfred/helpful it gives you even more stuff. If you're not sure what's the exact symbol/command/mode name you're looking for, there are 'apropos' set of commands. Also, absolutely learn Info and how to navigate it - it's enormously descriptive and very useful - it beats googling stuff up, because a) it works offline b) it gives you more accurate info about your current system.