Siva symbolically represents the tamasic quality. Because of this, he is called pasupathi, (the lord of the animals). His body color, which is white, denotes his purity (sivam) and association with the snowy mountains. His three eyes represent the sun, the moon and the earth, the three paths of liberation and the triple nature of creation. The third eye is actually the eye of wisdom or occult knowledge. The moon that adorns his head represents the movement of time and also his cosmic proportions. With the moon there, his head becomes the night sky, for which he earned the name Vyomakesa (one who has the sky or space as his hair). The moon also symbolizes his association with the occult and the tantras.
Siva is generally seated in yogic posture with which most Hindus are familiar. However we also come across Siva as nataraja or tandavamurthi in a dance posture. With his hair flying in all directions and hands and feet in dynamic motion, the image of nataraja is a symbol of harmony and rhythm. Among the objects, which are associated with him popularly, apart from the trident and the Damaru, are battleaxe (parasu), rosary (aksamala), pasa (noose), khatvanga (magic wand) and khadga (sword).
Lord Siva is know as Pasupathinath, the lord of all creatures. Being a lord of the animals he has complete control on their behavior. Since a snake is one of the most feared and dangerous animals in the world, the garland of snakes around the neck firmly establish the fact that he is a lover of animals and the animals always remain under his control.
Although universally acknowledged as one of the trinity gods of Hinduism, to His followers, He is Maheswara, representing the Trinity all by Himself, His different aspects manifesting themselves as the creator, preserver and destroyer of the worlds He creates. Symbolically He is worshipped as Lingeswara, which name stands more for His creative powers.
Historians believe that He was a pre-Vedic god who was admitted into the Vedic Pantheon because of His immense popularity during pre-vedic period. There is a theory that the seated yogi found on the seals of Indus Valley Civilization, was a prototype of Lord Shiva only. References to Him are found in the Rigveda.
In the Mahabharata we come across several references to Him. Both Arjuna and Krishna worshipped Him and obtained favors from Him. In the Ramayana too we come across several references to Him. Sage Valmiki depicted Ravana, the demon king and chief villain of the epic, as a great devotee and daily worshipper of Lord Shiva.
With the popularity of Saivism a great deal of literature grew around Him, which came to be recognized as Agama literature. So great was His popularity and fame that Agama literature was placed on equal footing to even the Vedas by His followers.
Saivism as a popular movement took shape mainly in South India because of the patronage of the Pallavas and the dedicated work of many great Tamil Saints, who built enormous bhakti or devotional literature in His honor and made His name a household name. Siva is also referred as the Lord of the south as he faces the south allways in his form as Dakshinamurthy.
Megasthanese mentioned the worship of Siva in his book Indika. So did Patanjali, the composer of Yoga Sutras. Two great rulers of ancient India, Kanishka and Harshavardhana were His great followers. In the south the Pandiyas, Cholas and Pallavas built many temples in His honor