Wall board for tile within tub/shower area

Just hired a contractor to install floor and wall tile. He mentioned 'yellow board' to install in tub/shower area as wall board behind tile. What is standard material or best to use in this potentially wet area? I was under the impression concrete board would be best. Thanks.

Any of the cement boards are fine but have certain requirements and they are not waterproof. There are also plastic foam boards available that are waterproof. Then there are the products clad with a waterproof covering. In addition there is plastic matting that is totally waterproof as well as liquid waterproofing membranes.

All of the above have different requirements for a proper installation.

Not sure what "yellow board" is, never heard of it. There is a product called Denshield that is a clad/waterproof board with yellow edges. The yellow edges mean nothing as far as I know and I have never heard it referred to as yellow board.

So in summary: Beats Me!

Seriously tho, don't hesitate to come back with more questions when you have more information and we will try to help.