A small portion of a program that’s set aside and given a name. It helps isolate keyA number used to encrypt (or encode) information so that no one can read it. Keys are used when encoding and decoding. You shouldn't have to mess with keys yourself. code in an easy-to-understand way, and it makes changes easier and less error prone. It’s a really important way to make programs easier to understand. May also be called a functionA small portion of a program that’s set aside and given a name. It helps isolate key code in an easy-to-understand way, and it makes changes easier and less error prone. It’s a really important way to make programs easier to understand. May also be called a subroutine..