Wikipedia encyclopedia describes Hindu mythology is a term used by modern scholarship for a large body of Indian literature that details the lives and times of legendary personalities, deities and divine incarnations on earth interspersed with often large sections of philosophical and ethical discourse.
Indian Mythology dates back to 7200 BC. It was then the first hymns of RIG VEDA were composed. Rig Veda celebrates beauty and elements of nature like Air, Water and Fire. The hymns converted them into elements of worship. Thus came the trio of the Hindu gods Vayu (Air), Agni (Fire) and Surya (Sun). Vedic gods are abstractions. Humans drew source of inspiration from their intangible and illusive qualities. It was in the Puranic stage that they reached a stage of individual incarnations. In these times the epics of Ramayana and Mahabharata were composed. These lead to the trio of Gods that Hindus worship till today. They are Brahma (the creator), Vishnu (the preserver) and Mahesh (the destroyer). The seeds of the Gods of today are in the Vedas.
Gods of the Trimurti
BRAHMA the creator (also known as Prajapati): After the act of creation, he has little prominence, often referred to as “grandfather,” aloof, unaware or unconcerned about the consequences of his actions. In one story he rewards even demons for their asceticism, thus causing much grief to the other gods. Brahma is sometimes said to be self-created, or born from a lotus out of Vishnu’s navel, or hatched from the cosmic egg. He is often depicted with four heads: as his daughter/consort Sarasvati tried to avoid his lustful gaze, other heads grew up in each direction she ran; when she ascended to heaven, a fifth head appeared, which Shiva cut off because of Brahma’s incestuous lust.
VISHNU the preserver of cosmic order (dharma): Represented with blue skin and four arms, often sleeping on a coiled serpent floating on the ocean. He rides Garuda, the sacred bird (symbol of Indian airlines today). As Vishnu became more important over the centuries, his “history” became more complex. The Puranas developed the idea of Vishnu having appeared on earth in nine previous avatars (or incarnations) during the present Great Age (Mahayuga), with one still to come (note that the number of avatari varies in the Puranas, some listing as many as 22, others say they are innumerable):
SHIVA the destroyer: Also god of fertility, gained prominence by destroying the city of demons; in one version he waited 1000 years until the cities, which rotated in the air, were aligned, then pierced all three with one arrow. He became so powerful because the other gods gave him their divine energy, which he kept after the battle (story in the Mahabharata). Shiva appears with a blue neck, because he swallowed the poison from the serpent Vasuki, which would have polluted the world ocean. He also has three eyes, for one day his wife Parvati playfully covered two of his eyes and the universe fell into darkness; he created a third eye to restore light. This eye destroys by fire. Shiva wears a necklace of skulls as “lord of goblins.” Dancing Shiva symbolizes the eternal movement of the cosmos, but also he dances to bring about the destruction of maya / illusion (i.e. this world) at the end of each kalpa (see great ages below).