ELI5: Explain Like I'm 5

Pick-up game

A pick-up game is when you and your friends decide to play a sport or game without organizing it beforehand. You might be walking past a park and see some other kids playing basketball, and decide to join in. There are no set teams or rules, and everyone just plays for fun. It's like playing with your toys at home, but outside with other people. It's a great way to make new friends and get some exercise!