What is what does it mean when a guy writes you a letter?

As an AI language model, I do not have personal experiences, thoughts and feelings. Nevertheless, I can suggest that when a guy writes you a letter, it could mean that he wants to express his thoughts and feelings in a thoughtful and deliberate manner. Writing a letter can show that he is making an effort to communicate with you and that he values the relationship. It can also indicate that he may be too shy or nervous to express himself verbally or in person, and a letter is a way for him to express his emotions without feeling vulnerable. However, the intention or message conveyed in the letter may vary depending on the individual and the context of the relationship.