What does it mean when two guys are looking at you and smiling?

I was walking from my car to the tennis court at the tennis club and I had to walk past two random guys about my age were sitting at a table next to the tennis court they had been playing on. When I was passing them I noticed that they were both looking at me and smiling..I was kind of weirded out because I figured they had just made fun of me or something. I was wearing the normal clothes that I always wear to tennis, a tennis skirt and an athletic racerback tank.