Lord Vishnu is mentioned as a sun god in Vedas (c.1800 - c.1200 bc). Over the next 1000 years or more, his importance grew and he became an amalgam of local cultic gods and heroes.
In mythology, Vishnu is worshipped as a preserver and restorer. His one hand holds a lotus (Padma), which is a symbol of a glorious existence.
The fourth hand holds a "Gada" indicating the power and the punishing capacity of the Lord if discipline in life is not observed.
According to Hindu tradition, he reigns in heaven with his wife, Lakshmi, the Goddess of wealth. God Shree Vishnu has four hands.
The first holds a counch shell (Shankha), which spreads the divine sound "Aum"; Other one holds a "Chakra" a reminder of the wheel of time and to lead a good life.
His vehicle is Garuda (eagle), which can spread the Vedic knowledge with great courage.
Lord Vishnu rests on the bed of a huge serpent, called, "SheshNag" which represents the sleeping universe. From time to time, he appears into this world, assuming a different incarnation each time to finish the evil forces.
Lord Vishu appeared in altogether 22 Avtars out of which 10 are principal Avtars as detailes below.
10 Principal Avtars of God Vishu
1-Matsya The Fish
The Matsya Avatar ie the Fish Incarnation is the first of the ten incarnations of Lord Vishnu. It has no significant representations in art and literature.
It shares with the rest of the world a generic belief that at one time the planet was threatened with a great flood and a savior in a boat preserved all life forms.
Also, it establishes the concept of Manu for each great age as defined in Hindu Mythology. The Manu and his wife became the first parents for each cycle.
In the fish incarnation Vishnu chose a great and pious king named Satyavrata to become the next Manu. And finally the task of this avatar was the most important of all, nothing less than the recovery of the lost Vedas.
2-Kurma The Turtle
Sage Durvasa had cursed Indra, the king of the Devas because he had insulted the sage's gift (a garland) by giving it to his elephant. Thus the Devas lost their strength, powers immortality and kingdom.
So they approached Lord Vishnu for help.
Vishnu advised them to drink the nectar to regain their lost glory and immortality. However, they had to struggle hard to achieve the nectar, since it was hidden in the ocean of milk.
After declaring a truce with their foes Asuras, Indra and his Devas together with the Asuras, used the serpent Vasuki as a churning rope and the mount Mandara as the churning staff.
When they began churning, the mount began sinking into the ocean. Taking the form of a turtle (Kurma), Vishnu bore the entire weight of the mountain and the churning continued and various objects were thrown out.
3-Varaha The Boar
Varaha is the third Avatar of the Hindu god Vishnu, in the form of a Boar. He apeareed to kill the demon, Hiranyaksha,who grabbed the Earth and carried it to the bottom of the cosmic ocean. The battle between Varaha and Hiranyaksha lasted for many years.
Varaha after winning the battle, replaced the Earth in to its place in the universe, by carrying it on its tusks. Varaha is th form, having a boar's head on a man's body.
In the latter form he has four arms, two of which hold the wheel and conch-shell while the other two hold a mace, sword or lotus or make a ose of blessing.
The Earth is held between the boar's tusks. The avatar symbolizes the safety of the Earth and the establishment of a new kalp cosmic cycle .God Vishnu married Earth (Bhudevi) in this avatar.
4-Narsimha The Man & Lion
Narsimha is the fourth Avatar of Lord Vishnu. It was taken in the Satyuga (last age) to kill the dreaded demon king,which was descendent of Hiranyakashyap.
Narsimha is the only avatar, which was Hybrid in form being half man and half animal. Lord Brahma had the blessings to Demon Hiranyakashyap, that no man or animal born naturally could kill him.
He has also blessing that he would not die in the day or in the night, on earth or in heaven, either by fire, water or by any weapon.
So, Lord Vishnu had to take avatar of Narasimha which was neither man nor animal and came out of a broken pillar, put him up on his thighs,laid hold of his teeth and tore him up in the middle with his claws. It was evening time - neither day nor night.
5-Vamana the dwarf Brahman
Vaman is the fifth avtar of Lord Vishnu who came to kill demon king Bali, the fourth lineal descendant of Hiranyakashyap. Bali, had defeated Indra and extended his authority over the three worlds.
Raksha Bali was great devotee of god Vishnu. All the gods worshipped lord Vishnu for protection and he assumed the Avatar of Vaman for the purpose of restraining Bali.
Once Bali was making a great religious offering, when Lord Vishnu in the form of Vaman appeared before him alongwith other brahmins.
Bali was overjoyed to see a holy man with such a diminutive form and offered him whatever he demanded. Lord Vishnu demanded for a land which he could measure by three strides.
Soon, Lord Vishnu as Vamana began to grow to a great height and with one stride he covered the whole earth, with his second stride he covered the entire sky and region above.
With the entire universe covered, Bali had no more land to offer. He bowed down in front of the Lord & offered his head for the third stride. Thus, Lord Vishnu regained the power from the demon king.
6-Parsurama The Sage With An Axe
Parshurama, the sixth avatar of Lord Vishnu appeared in the Tretayuga to destroy the warrior caste, kshatriya clan. When the kings of the earth became tyrant and started to torture people and saints.
Vishnu assumed the avtar of Parshurama and destroyed all the kings who were harassing the people. The main purpose of the avatar of Lord Parashurama was peace.
He wnted to make the earth free from the burden of cruel kshatriya kings by defeating the evilness of them as they neglected their regular duties as kings.
The kshatriya kings started performing anti-religious acts in the Satya-Yug. Goddess Prithvi (Mother Earth) was unbearable of all these evil acts and worshipped to Lord Shri Vishnu to relieve form this torture.
Lord Vishnu appeared in front of Mother Earth and assured that he will incarnate as Parasurama. Parasuram took the revenge of his father's brutal murder by finishing all the kshatriya kings.
Parasurama Jayanthi is observed on Vaishkha Shuddha Tritiya (third day of Shukla Paksha in Vaishakha Mas). This day is also celebrated as Akshay Tritiya.
7-Rama The Ayodhya Prince
Ram, the seventh avatar, who was the prince and king of Ayodhaya, appeared in the Tretayuga, to kill the demon king Ravan of Lanka. Rama fought a colossal war against Ravana's armies.
In a war of powerful and magical beings, greatly destructive weaponry and battles, Rama defeats Ravan in war and liberates his wife.
Having completed his exile, Rama returned to be crowned king,Lord Rama of Ayodhya. Rama became one of the most popular gods in the Hindu religion and was reffered to as 'Maryada Purushottam' means the 'limit of a good man'.
8-Krishna From Dwapar Yuga
Krishna, the eighth avatar of Lord Vishnu, appeared in the Dwapar yuga to kill the demon king, Kansa. Krishna told the epic poem Bhagavad Gita to the warrior Arjuna. Shri.
krishna stated, whenever religion or the law and order, is in trouble, I appear in this world to re establish the situation. I come to protect the people and to destroy the evil forces.
Lord Krishna conveyed the message of love and humanity to the world. Bhagwat Gita is sacred and holy book for the Hindus.
9-Buddha The Thinker
The ninth avatar, Mahavira Buddha, appeared in the Kalyuga, 'Buddha' means 'the enlightened one'. He taught the lesson of following a middle path in life.
He also advised that all sorrows come from emotional attachments and desires, so it's better to stay away from all such attachments to be happy.
As per the astrology, Buddha's incarnation is connected to Mercury, the planet of intellect and communication and symbolises intellectual potential.
When earth's rulers and citizens were taking pride in torturing life forms, Vishnu felt that it was time to teach them about compassion and non-violence towards both humans as well as animals.
Accordingly, he incarnated as Buddha in Kapilvastu in 6th century BCE.
10-Kalki From Current Yuga
Kalki, is the tenth Avatar of Lord Vishnu, which represents 'Eternity" or "time' or "The Destroyer of foulness". Kalki is yet to appear on the earth.
The avatar is expected to appear at the end of Kali Yuga. At the end of Kali-yuga, when there exist no topics on the subject of God, even at the abodes of saints.
The respectable gentlemen of the three higher castes and when nothing is known of the techniques of sacrifice, even by word, at that time the Lord will appear as the supreme chastiser.