Business casual is what grown-ups wear to work when they don't need to wear fancy clothes like a suit, but they still need to look nice and put together. It's like dressing up a little, but not too much.
For boys, this might mean wearing nice pants like khakis or dress pants, but not jeans. They can also wear a shirt with a collar like a button-up shirt, but they don't have to wear a tie or a suit jacket.
For girls, this might mean wearing a skirt or dress that is not too short or revealing, or pants that look nice but not like something you would wear to play outside. They can also wear a nice blouse or sweater, but they don't have to wear anything too fancy or sparkly.
Business casual is a little different from what you would wear to school or to hang out with friends, but it's still comfortable and lets you move around easily. When we dress nice for work, it helps us feel confident and ready to do a good job!