Shiva is worshipped in the form of Linga at the temple. Literally shiva means auspiciousness and Linga means a sign or symbol.
shiva also means "one in whom the whole creation sleeps after dissolution. shiva is the embodiment of tamas, the centrifugal inertia, the tendency towards dispersion, toward disintegration and annihilation. When the universe expands indefinitely, it dissolves and gradually ceases to exist. That dispersion in the obscurity of the causal insubstantially is the end of all differentiation, of all places and time. Nothing that has existence can escape the process of destruction.
Existence is only a stage of an expanding i.e., disintegrating universe. It is from destruction that creation again rises, hence destruction is the ultimate cause, the unmanifest origin of creation. shiva, the power of disintegration alone remains in the beginning and the end. The Linga installed in a temple is called achala Linga and is usually made of stone. It has three parts: the lowest part which is square is called Brahmabhaga and represents the Brahma the creator, the middle part which is octagonal is called Vishnubhaga represents Vishnu the sustainer. These two parts are embedded in the pedestal. The third, the Rudrabhaga which is cylindrical and projects outside the pedestal is the one to which worship is offered. Hence it is called Pujabhaga.
Pujabhaga also contains certain lines, technically called 'Brahnasutra' without which Linga becomes unfit for worship.