Weapon families are used in the AI design file to tell the AI wich weapon to use.
Sentry is used to skip ships that are supposed to stay where they are when you use the next/prev ship buttons. Some people like to manage their ships that way.
Take a look at Atraikius 'Cheat Sheet'
here
Many custom races have their own speech files. It can add a lot to the game. Please post them.