The biblical book of Isaiah 34:14 possibly describes lilith as a demon:
“And the wild-cats shall meet with the jackals, and the satyr [the
Hebrew is sei’ir, which means “goat”] shall cry to his fellow; yea,
the lilith shall repose there, and find her a place of rest.”
In the Dead Sea Scrolls (Qumran, 67 C.E.), the Seductress says:
“I, the sage, declare the grandeur of His radiance in order to
frighten and terrify all the spirits of the ravaging angels and the
bastard spirits, demons, liliths, owls….”
The Talmud suggests she is a demon ( Babylonian Talmud, Shabbat 151b, states she “takes hold of whoever sleeps alone in a house.”
The second Alphabet of Ben Sira seems to say that in Genesis 1:27, Adam and Eve were simultaneously created “male and female created He them.” In 2:21–25, states that Eve was formed from Adam’s tzeila, “side” or “rib.” Ben Sira suggests that Genesis 2:21–25 was referring to Eve while Genesis 1:27 is referring to Lilith.
Ben Sira then recounts a graphic story where Lilith, Adam's equal, requests to be on top during intercourse. When Adam rejects her request she says the Ineffable name of G-d and flies away. Many say she is responsible for the many demons who plague Eve's descendants. Since Eve was a part of Adam, she is submissive to him.
In Rabbi Isaac Hakohen's book The Emanation of the Left Side, he explains that good is derived from the ten emanations, sefirot, flowing from the right side of G-d (this is the feminine aspect of G-d ending with the shekhinah and malkhut); and evil from ten foul sefirot of the left side. Samael, Satan, is from the left.1 According to Rabbi Isaac, Lilith is the wife of Ashmedai, the prince of demons. Also, the tenth emanation of the left is Lilith.
The Zohar relates that Lilith had an adulterous 130-year relationship with Adam. This accounts for the many demons in existence.
Lastly, some scholars think that Lilith's origins are derived from Assyrian-Babylonian myth.
 To see a different approach to the concept of Satan, demons, and evil, please see this answer here.