Can you give us the context in which you heard it?
Let's say your grandmother gave you $10. "Save it for something special," she might have said. That means that you shouldn't spend it until you have something that is really worth buying.
Perhaps someone gave you a bottle of really, really expensive wine. You decide to save it for a special occasion. When your daughter announces her engagement. You and your spouse and daughter and future son-in-law share this fine bottle of wine.