Craft service is not catering

Pretty much just what the title says.

If you're working hard on a movie set, especially one with a reasonably solid budget (the new installment of Pirates vs. Dinosaurs vs the Harlem Globetrotters, perhaps) then round about noonish a catering truck will deliver a few meal options for your lunching pleasure.  A few hours later, you may once again be feeling peckish (those basketball game scenes vs the velociraptors really take it out of you), but the caterers are long gone.  The tables of water and snacks (fruit, chips, maybe some cold cuts if you're lucky) are provided instead by craft services, which is apparently a completely different operation, run by different people, and possibly even with a different union.