What is bok choy?

This week has been very busy so far. I started weight watchers this week, and I'm actually attending the meetings. So on Monday, I went to the meeting and got all of the materials I needed, including some recepie books. So I was looking at the recepie books and there are some interesting foods that they want you to cook with. So I was at the grocery store and I was wandering around the produce section, looking for a certain vegetable called bok choy. I could not find this thing anywhere. I went up to the man who was stacking vegetables, and asked if they had any bok choy. He kindly pointed it out, and gave me a funny look, because it happened to be directly in front of me. I didn't know what bok choy looks like! Other items on the list included shallots and scallions. I didn't know what either were (I still don't know what scallions are) and luckily I happen to stumble upon the shallots. And, after all that I forgot to get soy sauce. Anyways, I am interested to see how these recipes turn out.