According to Hindu Mythology, Lord Vishnu plays the role of the preserver of the Universe. He is also a member of the Hindu Trinity, the others being Lord Brahma and Lord Shiva. According to Vishnu Sahasranamam Vishnu is considered as the supreme god and worshipped with great reverence. In order to protect and preserve the World Vishnu manifested to the world in a variety of forms, called Avatars. According to the Bhagavad gita, whenever evil gains ascendance, God incarnates on earth to restore dharma, punish the evil and protect the weak and the righteous.These avatars are famous as ‘dasavatar’ or the 10 avatars of mahavishnu. These incarnations are Matsya , Kurma, Varaha, Narasimha , Vamana , Parashurama, Rama, Krishna, Buddha and Kalki. Among these nine of them have occurred in the past and the last one is supposed to take place at the end of Kali Yuga. Vishnu is worshipped as himself or as Lakshmi-Narayana along with his consort Lakshmi, the Goddess of Wealth. He is also worshipped as any of his avatars. Sri Salagrama is worshipped as a symbol of Vishnu in Hindu households.

Lord Vishnu is normally seen reclining on the great serpent AdiShesha or Ananda in the Ocean of Milk which is why he is also known as Ananta Padmanabha. The lotus of the creative power springs from his navel. The color of his body is that of the dark clouds. Vishnu has four hands, each holding a conch shell, sudarshana chakra, mace and lotus respectively. Around his neck he wears the auspicious Kaustubha gemstone. His vehicle is the Garuda. Vishnu Mantra forms the part of prayers offered to the lord. Given below are some of the mantras of Lord Vishnu.

“Om Namo Bhagavate Vasudevaya”

"Om Namo Narayanaya"

"SHAANTAAKAARAM BHUJAGASHAYANAM
PADMANAABHAM SURESHAM

VISHWAADHAARAMGAGANASADRASHAM
MEGHAVARNAM SHUBHAANGAM

LAKSHMIKAANTAM KAMALANAYANAM
YOGIBHIRDHYAANAGAMYAM

VANDE VISHNUM BHAVABHAYAHARAM

SARVALOKAIKANAATHAM ".

Vishnu- Gayatri Mantra

"Aum Narayanaye Vidmahe
Vasudavaye Dhimahi
Tanno Vishnu Prachodayat".

Also See

Avatars of Lord Vishnu (1-6) - Part 1

Avatars of Lord Vishnu - Part 2