I've heard of it. Its a very flexible type of adhesive used for going over substrates that have flex, or give, like a not too solid floor that bounces when you walk on it. the main benefit of it is to prevent the tile from cracking due to too much movement. It is expensive stuff, never worked with it though, but have used the next level down of 2 part adhesive, which is the powder and latex type, very sticky stuff needed for large wall tile, the size around 10 x 16 type.