Guy used to like me....i moved and now he poked me on facebook?

There was this really sweet guy in one of my classes at school and he liked me but he was always shy and so was I. He told his friends and they always used to tease him about it. He was still nice and we talked a little in school and he would try to flirt and wave or say hi in the hall and he shared a cupcake at a bake sale with me one day after school. He even started doing things like hugging me or giving me piggy back rides. But then I moved and we just stopped talking after that. Then two days ago when I went on facebook and he poked me. So I poked him back to humor him and now he poked me back haha. What was the point of him poking me? What does a poke do haha?