The following is a simple explanation:
Most adjectives can go in two main places in a sentence: in the attributive position and the predicative position.
"attribute / attributive" adjective means preceding the word it qualifies or modifies and expressing an attribute, as old in "the old dog" (but not in the dog is old ) and expiration in "expiration date" (but not in date of expiration ).
"predicate / predicative" means the part of a sentence or clause containing a verb and stating something about the subject (e.g., went home in John went home ).
In the attributive position, an adjective comes before the noun it modifies.
She is a nice girl.
She married a rich businessman.
In the predicative position, an adjective goes after the verb.
She is nice.
He looked upset.