Lord Shiva and Nandi are inseparable. Nandi, also called Nandikeshvara and Nandishvara, is the name of the gate keeper of Kailasa, the abode of Lord Shiva. He is usually depicted as a bull which also serves as the mount to Shiva. He is one of the Gana of Shiva. Nandi is the bearer of truth and righteousness. The word Nandi has come from Tamil root word Nandhu means to grow, to flourish or to appear which was used to indicate growing fluorished white bulls as well as divine bull nandi. The Sanskrit word nandi has the meaning of "happy", "joy" and "satisfaction"; also said as the properties of divine guardian of Lord Shiva - Nandi. Almost all Shiva temples display stone images of a seated Nandi, generally facing the main shrine.

Nandi is described as the son of the sage Shilada. Shilada underwent severe penance to have a boon ; a child with immortality and got Nandi as his son. It is said that Nandi was born from a Yajna performed by the Shilada and his body was clad in armour made out of diamonds when he was born. Nandi grew as an ardent devotee of Lord Shiva and he did penance to become the gate-keeper of the Lord Shiva as well as his mount. Nandi got the divine knowledge of Agamic and Tantric wisdom taught by Lord Shiva from goddess Parvati. 

He could teach that divine knowledge to his Eight disciples who are identified as the progenitors of Nandinatha Sampradaya - Sanaka, Sanatana, Sanandana, Sanatkumara, Tirumular, Vyagrapada, Patanjali and Sivayoga Muni. These eight disciples are directed to eight directions of the world by Nandinatha to spread the wisdom he taught them. There are many legends about Nandi. One describes his conflict with Ravana, the King of Lanka. Nandi cursed Ravana that his kingdom would be burnt by a monkey. Later Hanuman ji burnt Lanka when he went in search of Maa Sita, who was kept prisoner by Ravana in Ashok Vatika.