@shavecat To elaborate a bit (because I'm a little bored this evening): You pretty much don't ever need to be acting as the actual root user. Especially if you are new to Linux. There is a high chance of messing things up if you start working directly as the root user.
Instead, as we've mentioned, you should use sudo. But only when you need to! sudo stands for super user do. The super user is the root user. In other words: When you run a command with sudo in front of it, you are running it as the root user for just that one command. It's a nice way to elevate your rights temporarily when needed.
But I can't stress this enough: Don't run commands as sudo unless you absolutely have to! Any file or path that is created while sudo'ing, will be owned by root. And if that was not the intention, you will have issues later on, when the ordinary pi user tries to access those files or paths.
