The idea behind a pizza stone is to distribute the heat evenly accross the pizza base and secondly to extract the moisture, so that your pizza dough is crispy. Heat is important in the cooking process of a pizza: all breads need a high temperature to cook. The good news is that a pizza stone is a form of terra cotta and the cheapest ones work as effectively as the expansive ones.
In fact a home made pizza stone made from a terra cotta tile is perfect providing that it isunglazed. The theory is that because the pizza stone is made from natural clay it is porous it is capable of extracting the moisture from the pizza to ensure a crisp base. However its porous properties mean that basic care is necessary for the maintenance of a pizza stone. Make sure you don't use a glazed tile, they contain lead, what is very hazardous for your health.
The pizza can stick but a little cornmeal rubbed on the pizza stone before it gets heated can prevent the finished pizza dough from sticking. Because it is porous it does absorb other things such as soap and oil, which means that they should never be washed with a detergent, only with cool water.