What is a cat tree?

Last weekend, I went to my friend's birthday party and it was a blast. It was filled with laughter and fun. The best entertainer that night was actually their 2 yrs old son. We were amazed by his ability to talk and even to his mom's friends whom he met only once. He's not shy at all and he was quite a good host I would say. While I was chit chatting with the adults, he came over to me and told me that he bought his mom cat trees for her birthday because he knows his mom loves cats and he told me that cat tree would be the best gift for her and her little kitty cat named Smooches. Such a lovely little munchkin eh?