My mom and dad: KIDS COME DOWNSTAIRS TO EAT! Me: What's for dinner? Mom and Dad: Food.
The next day KIDS COME DOWNSTAIRS FOR FOOD! My brother and sister: What's for dinner? Me: Food ;-;
Listen up, buttercup. The joke is that the parents are being cheeky by just saying "food" when asked what's for dinner. The joke is on the questioner because they already know they are coming downstairs for food.