Each jaw is independently held into the chuck so each jaw can be removed independently from the others. Note that each chuck jaw is numbered and that same number is located next to the groove on the chuck.

When reversing jaws, be sure not to force a jaw onto the guide rails with the screw. "Wiggle" or tap them in with a rubber or lead mallet

Jaws are generally considered outside or inside depending on which way the part is located on the jaws. There are some chucks that have the ability to remove the top part of the jaw and reverse it, without removing the master jaw. This makes setups much easier.