Platao: No Qareen doesnt mean a spirit, As per Islamic methology each person is having two angels deployed over each of his shoulder to keep a note of his good and bad deeds similarly a Qareen is also deployed to try and keep him off the good path. Qareen is said to be a desciple of satan most probably a Genie made of smokeless fire.

So when a guys deceased the angels duty is over but this qareen will continue on earth thats the reason it can tell all about even a deceased person's extremely hidden secrets and appearing in the form of deceased person or sounding like him is nothing difficult for him.

In Asia or subcontinent this entity is also known as Hamzad.

Most of fortune tellers are using him to know about your past when you are visiting them, specially people who are good in possesing a Genie they will give you any detail of your past just with the help of this entity.