Descriptive adjectives are exactly what they sound like: they describe things. In fact, several adjectives can describe the same thing.
Now, we know what you're thinking: "Shmoop, that's great that I can use 37 adjectives to describe the horrible smell coming from my gym shoes, but where do I put them all?"
That's easy. A regular adjective appears right next to the word it modifies. A predicate adjective comes after a linking verb and describes the subject of the sentence.