A bird bath is just something the birds can bath in. Thomas has a little plastic bath tub, its so cute they should sell them at petsmart. I usually put a little water in my bathroom sink and put the birds on the counter and if they want to play in the water they will if not when I put them back in the cage I give them the little plastic bath tub. There are alot of diferent types of bath tubs, some go on the floor of the cage and some hang on the side of it.