In Hinduism, there are 10 avatars (incarnations) of Lord Vishnu that are considered the most significant. These avatars are:

1. Matsya Avatar - In this avatar, Lord Vishnu appeared as a fish to save the world from a great flood.

2. Kurma Avatar - In this avatar, Lord Vishnu appeared as a turtle to support the weight of the world and the gods during the churning of the ocean.

3. Varaha Avatar - In this avatar, Lord Vishnu appeared as a boar to rescue the earth from the demon Hiranyaksha who had taken it to the bottom of the ocean.

4. Narasimha Avatar - In this avatar, Lord Vishnu appeared as a half-lion and half-human to kill the demon king Hiranyakashipu who had obtained a boon that made him invincible.

5. Vamana Avatar - In this avatar, Lord Vishnu appeared as a dwarf to outsmart the demon king Bali and regain control of the universe.

6. Parashurama Avatar - In this avatar, Lord Vishnu appeared as a warrior sage to kill the corrupt and oppressive ruling class of kings.

7. Rama Avatar - In this avatar, Lord Vishnu appeared as a prince to vanquish the demon king Ravana and restore righteousness to the world.

8. Krishna Avatar - In this avatar, Lord Vishnu appeared as a cowherd to teach humanity the path of righteousness and to guide them towards spiritual liberation.

9. Buddha Avatar - In this avatar, Lord Vishnu appeared as Gautama Buddha to spread the teachings of non-violence and compassion.

10. Kalki Avatar - In this avatar, Lord Vishnu is yet to appear. He will appear at the end of the current age of darkness and chaos (Kali Yuga) to destroy evil and restore order and righteousness to the world.

These avatars are considered to be divine incarnations of Lord Vishnu, who takes on different forms to protect and guide the world in times of need. They serve as an inspiration and a source of guidance for Hindus in their spiritual and moral journey.