Nandi is the sacred bull calf, gatekeeper, and vehicle (vahana) of the Hindu god Shiva.
Sculptures of Nandi are a common sight at Hindu temples dedicated to his master, and he is partly responsible for the Hindu reverence for living bulls even today. A statue of Nandi is present as a bull sitting on a plinth in front of most Hindu temples dedicated to Shiva. The bull is often dressed by worshippers with bells, clappers, and a necklace of flowers.
Symbolically, the seated Nandi towards sanctum in Shiva temples, represents an individual jiva (soul) and the message that the jiva should always be focused on the Parameshwara. From the yogic perspective, Nandi is the mind dedicated to Shiva, the absolute. In other words, to understand and absorb light, the experience, and the wisdom is Nandi, which is the guru within.