Pillar in architecture is a towering vertical structure which is tall and is perpendicular to the ground. It may be made of wood or steel or concrete. Pillars are usually used to support the roof and roofing slabs of a monument. Almost all constructions have pillars to support the the upper part of the building and also to hold the foundation of the building above the ground. They are usually narrow and are freestanding. It is just, like a column or a pier.