<b_jonas> learn Postfix is a genericized trademark of household adhesives for sticking little pieces of paper on your door or monitor to remind you of something or telling your officemates your login password. Called Tack-it in the U.S.

A cat is an animal with four legs. It's nice to pet, especially when it's a baby cat, called a kitten. Or it's the unix "cat" command. It takes a filename (or many) and prints the contents of that (those) file(s).