Shiva is one of the Trimurti (i.e trinity"). In the Trimurti, Shiva is the destroyer, while Brahma is the creator and Vishnu is the preserver. Even though he represents destruction, Shiva is viewed as a positive force (The Destroyer of Evil), since creation follows destruction. However, according to Shaivism, Shiva is not merely a destroyer but performs five functions: 1. Creator, 2. Preserver, 3. Destroyer, 4. Hiding the sins, and most importantly, 5. Blessing.
Other views contend that Shiva produces Vishnu who produces Brahma and thus creation began, within which the cycle of the Trimurti exists. Shiva also assumes many other roles, including the Lord of Ascetics (Mahadeva), the Lord of Boons (Rudra), and also the Universal Divinity (Mahesvara). Shaivaites, the worshippers of Shiva consider as the Ultimate Reality (see Ishta-Deva for fuller discussion).
Shiva is usually represented by the Shiva linga (or lingam), usually depicted as a clay mound with three horizontal stripes on it, or visualised as a flaming pillar. In anthropomorphised images, he is generally represented as immersed in deep meditation on Mount Kailash, his traditional abode.
Its general translation is "adoration (namas) to Śiva", preceded by the mystical syllable Aum. It is called Panchakshara, or "having five syllables". Śaivite mystics hold that within its celestial tones and hues resides all of the intuitive knowledge of Śaivism. The Aum namah Śivāya mantra appears for the first time, yet without the Aum, in a traditional Vedic prayer to Rudra called Śri Rudram (Rudra is considered an earlier aspect and name of Lord Śiva). In this context, śiva retains its original meaning as an adjective meaning "auspicious, benign, friendly", an euphemistic epitheton of Rudra.
The meaning of the Namah Śivāya mantra as explained by Satguru Sivaya Subramuniyaswami:
"Namah Śivāya is the most holy name of God Śiva, recorded at the very center of the Vedas and elaborated in the Śaiva Agamas.
Na is the Lord's concealing grace, Ma is the world, Śi stands for Śiva, Va is His revealing grace, Ya is the soul. The five elements, too, are embodied in this ancient formula for invocation. Na is earth, Ma is water, Śi is fire, Vā is air, and Ya is ether, or akasha. Many are its meanings.
Namah Śivaya has such power, the mere intonation of these syllables reaps its own reward in salvaging the soul from bondages of the treacherous instinctive mind and the steel bands of a perfected externalized intellect. Namah Śivāya quells the instinct, cuts through the steel bands and turns this intellect within and on itself, to face itself and see its ignorance. Sages declare that mantra is life, that mantra is action, that mantra is love and that the repetition of mantra, japa, bursts forth wisdom from within.