The scrotum feels different than the balls themselves. The balls tend to hang towards the bottom of the scrotum, and if you are just fondling the top of his scrotum what you feel will feel like extra skin (as you pointed out). But if you cup the entire scrotum in your hand and "massage" you will locate his testicles. Mrwiggles is correct in saying that they feel like eggs. They feel like eggs inside a bag and they can roll around and guys typically enjoy them being played with gently!