cd
cd [-L|-P] [dir]
cd changes the current directory to the one specified.
Essential for making your way around the filesystem. You'd be stuck without it. On the face of it a very simple command, but with few tricks up its sleeve to make navigation more efficient.
Examples
Change to previous directory
cd -
Change to home directory
cd
Change to subdirectory of home directory
cd ~/Desktop
Change to subdirectory of other user's home directory
cd ~ripley/Desktop
