origin: [Biblical] Arabic; قرين qarīn= companion.
Do you feel a presence even when you're alone?
Have you had thoughts that felt like they were not your own?
This sensation has a distinct name and tradition in the Muslim world, a qareen; an invisible companion that you are tied to for life and from birth. Sort of the opposite of Christian tradition's Guardian angel, Qureens are commonly held to be from lower realms, and instead constantly temp people away from the path to righteousness; example: if you see a person in need and turn away, a qareen could be seen as implicit in that.
However, the true tone of the qareens is debated due to the original Arabic text in the Q'ran, some say there are GOOD and BAD qareens or that they reflect the nature of their partners. Muhammad himself managed, with the help of Allah (God), to convert his qareen to Islam, thus assuring the purity of its nature forever more. In fact, it is also said, that during ramadan, the qureen are chained and preventing from bothering man, for it is written that ramadan is a time when certain worlds are separated from another.
Allah's Apostle (صلی الله علیہ وسلم) said, "When the month of Ramadan starts, the gates of heaven are opened and the gates of Hell are closed and the shaitaans are chained."
jinn or djinn [jĭn]:
origin: [Biblical] Arabic; janna = hide or conceal.
Qareen are part of the world (or species) of Jinn; supernatural beings that co-exist with us, although they come from another realm or dimension. In Western culture, genies are seen as playful characters, but in their original context, undiluted by exoticism, genies or jinn are demons who wish ill upon humans -- hence why your wishes never quite go as you may expect. Jinn are especially dangerous because they are intelligent, have free will, and can look similar to humans (when not invisible).
It is written in the Quran & the Sunnah (the traditional portion of Muslim law):
“Indeed We created man from dried clay of black smooth mud. And We created the Jinn before that from the smokeless flame of fire” (Quran 15:26-27)