Shedim is the Hebrew word for demons. The word shedim appears only twice (always plural) in the Tanakh, at Psalm 106:37 and Deuteronomy 32:17. It was possibly a loan-word from Akkadian in which the word sedu referred to a protective, benevolent spirit. Both times the term appears in the Tanakh, it deals with child or animal sacrifice to false gods that are called demons. The word may also derive from the "Sedim, Assyrian guard spirits" as referenced according to lore "Azael slept with Naamah and spawned Assyrian guard spirits known as sedim".
Folklore and Kabbalah
Shedim are said to have had the feet and claws of a rooster. According to one legend, the shedim are descendants of serpents, or of demons in the form of serpents, alluding to in the serpent in Eden as related in Genesis. To others they are descendants of Adam and Lilith. Another legend said that God had started making them, intending for them to be humans, but did not complete their creation because He was resting during the Sabbath. Even after the Shabbat, He left them how they were to show that when Shabbat comes, all work must be viewed as complete.
Supposedly, sinful people sacrificed their daughters to the shedim, but it is unclear if the sacrifice consisted in the murdering of the victims or in the sexual satisfaction of the demons. To see if these demons were present in some place, ashes were thrown to the ground or floor, and then their footsteps became visible.
The shedim are supposed to follow the dead or fly around graves.
There are many things that one is admonished not to do in order to avoid invoking shadim, such as whistling or even saying the word "shedim." Rabbi Yehudah HaChasid wrote in his tzavaah that one should not seal up windows completely because it traps shedim in the house.