Whenever the world has lost its order, Lord Vishnu has appeared as an incarnation to get it back to Dharma. According to Hinduism, Lord Vishnu has appeared in 24 forms till now and established the superiority of Dharma over the Adharma. Here is a list of the various forms that Lord Vishnu has taken until now. Have a look at them.
This is the avatar in which Lord Vishnu is seen as half man and half fish. He rides a boat, which is made of knowledge. Riding on the same boat of knowledge, he also saves his devotees. It was on the same boat that he had saved Manu. Once a demon sees the boat and steals it away. He even tries to destroy the boat, but till then Lord Vishnu comes for rescue and saves the boat from the clutches of the demon. This signifies how unawareness tries to hold us in its clutches. Man must give himself to the service of God and defeat the demon of unawareness with knowledge.
This is the avatar in which Lord Vishnu appears as a turtle. In many depictions, he has been shown as a half man and half turtle. Once when a sage had cursed the Gods that they would lose all their powers. Fearing this, they discovered a remedy to get their powers back. They started churning the ocean of milk to make a nectar that would make them immortal. They had to churn the milk of the ocean using a huge mountain. Now, how could they churn the whole ocean, using the mountain. Lord Vishnu then took this form as a turtle and bore the mountain on his back, so that they could churn the cosmic waters.
This is described as the third avatar of Lord Vishnu in the Dashavataras. He took form as the Varaha when the demon king Hiranyakashyapu lived on the earth. The earth personified as Bhudevi approached Lord Vishnu for help as all the inhabitants on the earth had started sinking in waters because of the tyranny of the demon king Hiranyakashyapu. Lord Vishnu then appeared as Varaha and lifted the earth on his tusks and thus saved her and the inhabitants from the cosmic waters.
Lord Vishnu had appeared in the form of half lion, half man to save the devotees from the demon king Hiranyakashyapu, who was the father of Hiranyakashyapu, as discussed above. When this king had acquired a power such that he could not be killed by a man or an animal, in day or at night and neither inside the house nor outside. Lord Vishnu then took this form, in which he was neither a man nor an animal. He killed him at a time when it was the dusk, neither day nor night and the place was just the entrance of the house, which was neither inside nor outside. Lord Vishnu, killed the demon using his power and intelligence together.
Vishnu appeared in his fifth avatar as the dwarf named Vamana. When the demon Mahabali had acquired disproportionate share of the universe, he was very happy and organised a gift-giving ceremony for all the famous saints. Maharishi Vamana also appeared there. When Mahabali asked this sage to accept as much wealth as he wanted as a present from Mahabali, Lord Vishnu in the form of Vamana only asked for three pieces of land. Mahabali agreed to give him that. So, Lord Vishnu immediately became a giant and in one step he covered the earth; in the second, he had covered the sky and there was no space left for the third piece he had asked for. Mahabali, bound by his promise, had to offer his own head to Lord Vishnu. As Lord Vishnu stepped on it, Mahabali died and reached the Patal Loka.
Lord Parashuram was the sixth Avatar of Lord Vishnu. When the earth was largely occupied by the tyrant Kshatriya kings, mother earth, the earth Goddess, then again approached Lord Vishnu for help. Lord Vishnu, took the form of Lord Parashuram and destroyed the rule of the tyrant kings. It is believed that he even killed the successors of these demonic kings and saved mother earth twenty one times from them.
Lord Rama was the seventh incarnation of Lord Vishnu. He took birth as the son of King Dasharatha and to his wife Kaushalya in Ayodhya. When the demon king Ravana had once kidnapped Rama's wife Sita, Lord Rama went to her rescue and defeated the demon king to establish the order back in the world.
Lord Krishna was the eighth incarnation of Lord Vishnu. He was born as a son to Devaki and Vasudeva. His aim was also to bring back the order in the universe. While he killed a number of demons that tried to attack him, his main aim of life was to re-establish the cosmic balance of Dharma by guiding Arjuna, the hero of the battle - Mahabharata. He motivated him soon before the war, when Arjuna was not able to build up the courage for killing his own kins. His long narration and explanation of Dharma, is now followed as Geeta by the Hindus.
Lord Buddha has been described as the ninth incarnation of Lord Vishnu, according to Hinduism. He was born as king Siddhartha to King Shuddhodhana and his wife Maya Devi. He became a hermit at the age of 29 years and found the true meaning of life through enlightenment under the Bodhi Tree at the age of 35 years. This way, he guided and still guides the generations towards righteousness and salvation through the eight-fold path. He is the founder of Buddhism.
It is believed that Lord Vishnu will appear in his tenth avatar as Kalki, riding a white horse. He will once again re-establish the cosmic order and save the earth from the evil time of Kali Yuga.