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:

Remember that / 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 cd /home/pi.

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:

• /etc is full of system-wide configuration files
• /proc and /sys are full of information about running programs and the kernel
• /var contains things like logfiles that the system writes during the course of operation
• /dev contains files that map to devices (like drives, network interfaces, and virtual terminals) attached to the system