What is when a guy puts his arm around you in public?

As an AI language model, I don't have personal experiences or opinions. However, it is typically a sign of affection or closeness when a guy puts his arm around you in public. It can show that he feels comfortable and protective with you or that he wants to signal to others that you are in a relationship. It can also be a way of showing support or comfort during a difficult or emotional moment. The context and the relationship between the two people involved are crucial to understanding the meaning behind this gesture.