Shiva is depicted as a Yogi, covered in the ashes of his sacred fire which represent the burning of all attachments and identifications.
For many Yogis and Tantric adepts, and of course, for all Shaivites (traditional devotees of Shiva), Shiva (or 'Siva', depending on the way the word is transcribed from the Sanskrit alphabet) is honoured as the Absolute Divine principle.
Yoga and Tantra are often connected to stories of Shiva and his consort Shakti Devi (also known by many names in different forms or incarnations such as Sati or Parvati).
Shiva means literally, "the 'Auspicious One", or Beneficent One, meaning the source of Divine Blessings.
He is also known by many other titles such as Shambo (or 'Shambhu'), meaning the Abode of Joy.
Whether the Hindu 'gods' or 'devas' (meaning literally 'Resplendent' or 'Shining Ones') are just symbols or are actually objective 'Beings' is controversial.
The spiritual masters of India have expressed various views on this.
For a clearer understanding of the 'gods' in Hindu spirituality, see the article on 'Devas' - the 'Radiant Ones'.