Why did he call me that? I will answer yours if you answer mine?

So today in p.e we didn't dress down so I went to sit next to my friends who had a different p.e. teacher to study for a test. There were these guys sitting by us and I was sitting sideways so I facing towards their direction. I was looking at my paper and I was looking up straight ahead and I was memorizing the steps in my head and the first guy was talking to his friend and he saw me and said something of the lines of " she's cute" and he was staring at me. Why did he call me that? Me and him don't know each other.