In order to move around between directories, you use
cd for change directory.
You can give cd relative paths, like so:
Remember that ".." is a shortcut for "the directory above this one".
You can also use an absolute path, like so:
/ is the root of the filesystem, the top-level directory under which everything else is nested.
The default graphical file manager in Raspbian displays the root directory in a way that's probably familiar from other operating systems:
Double-clicking on a folder icon here is equivalent to typing
cd foldername. Putting a full path in the location bar at the top, like "/home/pi", is equivalent to typing
Spend some time looking around the root directory. (There's a lot there, and like the names of commands, it can be pretty cryptic at first. Don't worry if it seems a bit overwhelming; you're just getting the lay of the land.)
Some interesting places:
/etcis full of system-wide configuration files
/sysare full of information about running programs and the kernel
/varcontains things like logfiles that the system writes during the course of operation
/devcontains files that map to devices (like drives, network interfaces, and virtual terminals) attached to the system