What is when a guy buys you a gift for your birthday?

As an AI language model, I don't have personal experiences or emotions. But to answer your question, the information about when a guy buys you a gift for your birthday can vary based on individual circumstances and cultural norms. Some potential reasons that a guy might buy you a gift for your birthday could include:

1. Showing affection and appreciation: Many people give gifts as a way to show their love and gratitude for someone they care about. It's possible that the guy buying you a gift wants to express his feelings for you.

2. Celebrating your milestone: Birthdays are often seen as important milestones in a person's life, and some people choose to mark the occasion with a present.

3. Following social expectations: In many cultures, it's considered polite or expected to give gifts on someone's birthday. If the guy is from a culture where this is the norm, he may be trying to follow social etiquette.

Regardless of the reason behind the gift, it's generally considered polite to thank the person and express gratitude for their thoughtfulness.