... is one paragraph at the bottom of page 80.
It tells you that you don't need to type the whole variable name. Just give it two-three letters, and hit the tab key. If you have variable names that have more than that many characters in common, Stata will fill out as much as it can and beep you. But usually you don't, so Stata will type out your variable name in its entirety! It's called "tab expansion" and I just discovered it by accident.