A goodie is a small treat or desirable item, something nice that makes people happy to receive. When a teacher hands out goodies after a successful class party, she might be giving out candies, stickers, or small toys. Birthday party goodie bags are filled with little treasures like bubbles, temporary tattoos, or chocolate.

The word has a cheerful, lighthearted feeling to it. People don't usually call expensive or fancy things goodies: a piece of candy is a goodie, but a new bicycle isn't. The word suggests something small, sweet, and fun rather than serious or important.

In movies and stories, people sometimes talk about “the goodies and the baddies,” meaning the good guys and the bad guys. This usage is more common in British English and sounds deliberately playful and informal.

You might also hear someone exclaim “Oh, goodie!” when something nice happens, like finding out there's extra recess or that dinner will be pizza. It's an old-fashioned but enthusiastic way of saying “hooray!” or “great!”