The following is a simple explanation:

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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.