What does it mean when a someone touches your thigh?

I was sitting next to a guy and he smacked my thigh unexpectedly and I was surprised because I was day dreaming. He did it again later and I didn't know what to do so I smacked his back then he didn't do it again. That day he had been flirting with me. What does that mean? Also, what does it mean when someone twirls their finger in your palm?