There are two types of Avatars- Sakshaty-Avatara and Avesa-Avatara. The Lord Vishnu`s avatars ofLord Krishna, Lord Rama, and Lord Narasimha are called Sakshaty-Avataraand the Lord Vishnu`s avatars of Naravada Muni, Parashurama, Vyasa, etc.
4. Narsimha-Hiranya Kashyap was a privileged demon not to be killed by any human or animal. He can neither be killed inside or outside the house, at night or day, on Earth or in the sky. Hence, Lord Vishnu incarnated himself as Narsimha, half lion and half-human form, to kill the devil at dusk at the entrance of his house. https://vedicfeed.com/wp-content/uploads/2019/02/Narasimha-Avatar-Vishnu.jpg?ezimgfmt=ng:webp/ngcb22
5. Vamana-The fifth avatar of Lord Vishnu is the dwarf Brahmin, Vamana. God took this form to check the demon king- Mahabali. The king has seized three different worlds. Hence, Vamana asked him for three feet of land. The king agreed to give away his head when he realized that he was Lord Vishnu. Vamana stepped over his head to grant him liberation. https://vedicfeed.com/wp-content/uploads/2019/02/mahabali.jpg?ezimgfmt=rs:720x450/rscb22/ng:webp/ngcb22