According to ancient period or Puranic period The Vishnu is the one of self created deity in the trinity or Trimurti ( Brahma, Vishnu, Mahesh,).We can say that the Vishnu is the master of the past, present and future, one who supports, sustains and governs the Universe and originates and develops all elements within Universe so, Vishnu governs the aspect of preservation and sustenance of the universe, so he is called “Preserver of the universe”.
Vishnu is a tall and handsome man, dark (or blue) in color . In his four hands, he holds a conch shell ( symbolizing the source of everything) , a disk or chakra (representing the universal intellect) , a lotus ( symbolic of universal beauty) and a mace ( symbolic of knowledge). The Kaustubha, a brilliant gem adorns his chest and dazzles with the light of all the natural luminous forces . His lock of hair called Shri Vatsa, is a sign of fortune . The Syamantaka jewel shines on his wrist . A lotus emerges from his navel and Brahma, the god of creation rests on top of it . He is often seen reclining in the lap of Shesh Naga, amidst the cosmic waters, with his consort Lakshmi at his feet .
The word Vishnu is formed from the Sanskrit root ‘vis ‘ which means to pervade, and accordingly, Vishnu is all pervasive and ubiquitous . His consort is Lakshmi, goddess of beauty, happiness and wealth(Dhan) . Their abode is heaven or Vaikuntha, he reclines on a multi headed cobra called Shesha Naga and his vehicle is the mythical bird Garuda.
Vishnu, in his role as Preserver, is the divine guardian of dharma denoting truth, right action and right behavior . He sustains the universe and whenever the natural order of things is disturbed or threatened, he assumes a human form with supernatural powers and combats the evil forces and restores orders . He lives in the world of mortals, has his share of happiness and sorrow, extends love and compassion and uses his cosmic powers to destroy the wicked . The forms assumed by him are called his incarnations(Avatars) and he instills a part of his divine self in each one of them . There are ten incarnations ( avatars ) of Vishnu. These include Meena (fish) , Narasimha (man lion) , Kurma (tortoise) , Varaha (boar) , Vamana (dwarf ) , Parshurama, Rama , Krishna, Buddha, and Kalki, who has not appeared as yet . Vishnu is a multi faceted god and some of his incarnations are widely worshipped . The four gateways to Heaven are all dedicated to some form of Vishnu .
Worship of Vishnu brings peace and quiet, awakens the goodness inherent within everyone and inspires man towards benevolent action . Even Yama, the god of death tends to be wary of the followers of Vishnu.
Vishnu is worshipped in different forms by his devotees . For those who believe in meditation, worship of god is Yoga. Those who believe in enjoyment of material things, worship him as Bhoga . Vira or Brave persons are the chosen form for those who want physical proficiency and Abhichakra is for kings who wish to be victorious . Vishnu is known as many names like, Narayan, Hari, etc.