To hull a strawberry means to remove its green calyx (you know, the leafy stem), which is pretty but no fun to eat.

It's a good idea to hull strawberries with a paring knife if you're making jam or a fruit salad. But you may want to leave them unhulled for presentation's sake if you're making a tart. If you're going to be eating them with your fingers, the calyx makes a nice little handle.

Bonus: The word hull is also a noun that refers to the outer layer of a seed or a fruit.

Recipe: Pan-Seared Salmon With Strawberry Salsa (hogwash)
Recipe: Baked Strawberry Pudding (Cook & Eat)