what are the nagas?

Nāga  is the Sanskrit and Pāli word for a deity or class of entity or being, taking the form of a very great snake — specifically the king cobra, found in Hinduism, Buddhism and Jainism. A female nāga is a nāgī or nāgiṇī

                                                             entomology

In Sanskrit, a nāgá (नाग) is a cobra, a specific type of snake (hooded snake). A synonym for nāgá is phaṇin (फणिन्). There are several words for "snake" in general, and one of the very commonly used ones is sarpá (सर्प). Sometimes the word nāgá is also used generically to mean "snake". It also can be a certain entity that takes the form of a snake sence sometimes the nagas can be huge snakes comonly associated to demonic entities but not all, sesha the world serpet on whos belly lord vishnu rest (image below) is not evil at all.

Mahabharata

In the great epic Mahabharata, the depiction of nagas tends toward the positive. An epic calls them "persecutors of all creatures", and tells us "the snakes were of virulent poison, great prowess and excess of strength, and ever bent on biting other creatures" (Book I: Adi Parva, Section 20). At some points within the story, nagas are important players in many of the events narrated in the epic, frequently no more evil nor deceitful than the other protagonists, and sometimes on the side of good.

The epic frequently characterizes nagas as having a mixture of human and serpent-like traits. Sometimes it characterizes them as having human traits at one time, and as having serpent-like traits at another. For example, the story of how the naga prince Sesha came to hold the world on his head begins with a scene in which he appears as a dedicated human ascetic, "with knotted hair, clad in rags, and his flesh, skin, and sinews dried up owing to the hard penances he was practising."Brahma is pleased with Shesha, and entrusts him with the duty of carrying the world. At that point in the story, Shesha begins to exhibit the attributes of a serpent. He enters into a hole in the Earth and slithers all the way to bottom, where he then loads the Earth onto his head. (Book I: Adi Parva, Section 36.)

Enmity with Garuda

The great nemesis of the nagas in the Mahabharata is the gigantic eagle-king Garuda. Garuda and the nagas began life as cousins. The sage Kasyapa had two wives (amongst his 13 wives, all prajapati Daksha's daughters), Kadru and Vinata, the former of whom desired many offspring, and the latter of whom desired few but powerful offspring. Each got her wish. Kadru laid 1000 eggs which hatched into snakes, and Vinata laid two, which hatched into the charioteer of Surya the sun god andGaruda. Through a foolish bet, Vinata became enslaved to her sister, and as a result Vinata's son Garuda was required to do the bidding of the snakes. Though compliant, he chafed and built up a grudge that he would never relinquish. When he asked the snakes what he would have to do in order to release his mother, Vinata, from her bondage, they told him he would have to bring them amrita, the elixir of immortality. Garuda stole the elixir from the gods and brought it to the serpents in fulfillment of their requirement, but through a ruse prevented them from partaking of it and achieving immortality. From that point onward, he regarded them as enemies and as food.(image below) (Book I: Adi Parva, Sections 16ff.