-ive is an adjective suffix that means "to have the nature of".
Examples:
Expressive=something that expresses
Extensive=something that extends
Creative=something that creates
Combative=something that combats
You use adjectives, of course, to modify nouns. So if I say, "You're a very inventive person," what I mean is, "You're the sort of person who invents things."
So to answer your question, not much changes. If a verb is something that you do, then an adjective ending in -ive means that the noun modified by it is known for its ability to do that verb. A secretive cat is a cat that has the nature of secrecy. An inquisitive woman is a woman who has the nature of inquiry (i.e. curiosity). A punitive law is a law that has the nature of punishment. The suffix basically means that the affected noun has a certain verb as an important quality.