So let's look at few things and how they should be handled to make sure that the grout you use compliments your beautiful tile. Do you know the difference between sanded and unsanded grout and where each should be used? Now the difference in the two is easy. One has sand, one doesn't.
What this mat does is provide a separation between the sub flooring material, whether that be wood or concrete so that if there is movement in the concrete/wooden sub floor, it will not translate up into the tile and grout and cause cracking.The mat will take the added stress of the movement below and not the tile/ grout therefore helping to eliminate cracking. For further reading about this product-http://www.schluter.com/Schluter-DITRA-XL.aspx
As we have pointed out before, planning ahead and armed with knowledge will lead to a successful installation as it is so much easier to do right the first time than have to go back and correct later.