What does it mean when a guy listens to your conversations?

I was talking to my friend in class who was sitting behind me. He was two rows across the and I can tell he was looking at me in the corner of his eye and looked like he was paying attention to my conversation. If it helps, I was talking about one of my guy friends and complaining about that to my friend. What does this mean? Also, he acts awkward around me and generally glances at me for a while now.
What does it mean when a guy listens to your conversations?
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