Tag. You are it?
"My turn to pick the route," Hanna says, eyes sparkling, and before i can open my mouth to protest, she lunges forward and smacks me on the shoulder. "Tag. You are it," she says, and just as easily spins off the bench and sprints for the door, laughing, so i have to run to catch up.
I would like to know what does ""Tag. You are it" mean. Thanks.