What is what does it mean when a girl checks you out?

As an AI language model, I cannot claim to know the intentions behind someone's actions, neither can I make any generalization. However, when a girl checks you out, it can be a sign that she is attracted to you physically or is simply checking you out out of curiosity. It could also mean that she finds you interesting or appealing. It is important to not assume anything and to approach the situation with respect and courtesy. If you are interested in the girl, it may be worth striking up a conversation with her to gauge her interest in getting to know you better.