The word rakshasa comes from the Sanskrit word for demons or malevolent spirits. So, the word itself tells you something about these creatures. They’re not friendly. At all. They like to eat people.
Rakshasa are vampire-like creatures of Hindu mythology. The legends on how they came to exist vary, like most of Hindu mythology. They may have sprung from the feet of Brahma, one of the Hindu Trimurti; the creator god. And feet are pretty much the worst part of the human body in Hindu tradition; they’re the lowest part of the body, and all you do is walk on them all day. Nothing good can come from feet, even the feet of a super awesome creator god.
By other traditions they are descendents of Kashyapa, the great rishi, or sage. Kashyapa is another one of the many creator figures in Hindu mythology. The rakshasa, as descendents of Kashyapa, are considered a type of Asura, the class of deities that are placed often in opposition with the Devas; the gods. So, think Titans versus Olympians.
Sometimes the rakshasa are described as being the original inhabitants of India, here long before humans. They are often classed with other divine spirits of Hindu lore, being more trickster-like in some stories. Other stories portray these spirits as being malicious and ill-spirited. They do have a divine element, like gods in themselves.
They were actually said to all have lived, at one point, in one part of the world, a wonderful place called Lanka. Lanka had been constructed by the divine architect, the god of all architects and craftsmen, Viswakarma. The rakshasa who lived in Lanka were all ruled, according to myth, by the ten headed demon-king Ravana. Ravana was the King of Lanka, and of all the rakshasa demons. Ravana is one of the most deplorable demons of the great Hindu epic, The Ramayana. Though, by other accounts he is a capable ruler of Lanka and even gained favor with some gods of the Trimurti. So he was possibly a wonderful leader… he was also a murdering rapist who ate people.
The rakshasa weren’t quite so powerful as Ravana, though they did have other similarities. The rakshasa tear people to shreds, and also by some accounts are every bit as lustful as the demon-king Ravana. The rakshasa are said by some lore to be restricted to roaming about at night only. They are especially active on the night of the new moon. Some of these creatures are able to shape-shift, so their true form is uncertain, but they are believed to be fanged beings who eat humans alive.
The rakshasa can also shapeshift and seem like some harmless owl, when really, they’re a monstrous, fanged, venomous creature just waiting to lure you in and rip your throat out.
Rakshasa are also said to be what people with terrible karma may be reincarnated as. This is similar in a way to some more recent ideas about people who were sinful in life being at risk for rising from the grave as a vampire.
The rakshasa are also believed to have the ability to possess corpses and use those bodies to feed on people. So even if you destroy the corpse, you have not destroyed the rakshasa demon.
Also, the rakshasa demons have a friend in a creature called the yatu-dhana. These bottom-feeders are nowhere near as powerful as the rakshasa. The yatu-dhana are scavenger vampires. They feed off of the scraps of bodies the rakshasa have already ravaged.