We call it as a "Palayok". This is used in old tradition of cooking of many Filipinos back then. Most foods being cooked on this kind pot are rice, fish with sour sauce, and veges.
Clay pots or "palayok" is made of clay which is a porous material. When the pot is saturated with water and put into the oven, there is a slow evaporation of steam from within the pores of the clay itself. During the cooking process, the food forms its own juices. These juices cannot escape until the pot is completely dry.
Fortunately, when the pot becomes dry, the food is cooked! Because wet clay does not become as hot as metal, it is necessary to cook at a higher temperature than is usual, (450ºF rather than the customary 350ºF). However, in spite of this high temperature, the danger of burning is minimal and can only take place if the food is cooked for too long a period of time.