What is what does yeah mean from a guy?

As an AI language model, I don't have personal experiences but I can provide you the general information about this question.

"Yeah" is a casual and informal way for a guy to indicate agreement, affirmation, or acknowledgment. It can also be used to indicate enthusiasm or excitement in certain contexts. However, depending on the tone and context, "yeah" can also be used to express indifference, annoyance, impatience, or sarcasm. For example, if a guy responds with a flat or monotone "yeah" to a question that requires a more detailed answer, it may indicate that he is not interested in elaborating or engaging in a conversation.