Gargoyles are the digusting carvings of faces and bodies of humans and animals. Serving originally as water spouts to direct the water away from a wall, they can often be found on (Gothic) buildings and churches. In medieval times, the function of Gargoyles changed. They became representations of religious events, created for the illiterate population to "read".
From the fact that Gargoyles are such hideous creatures stems the notion that they were created to avert evil. Placed on the outside of buildings supposedly kept evil out. In later times, most of them became mainly ornamental and served no other purpose than decoration.