a person possessed by a jin:
it means that an alien creature has invaded your soul and they have the ability to get into the human soul as they are made of fire the element of air they can enter the body by nails through mouth ,but there are three stages in which they can invade a body.
1)in extreme happiness when a person is laughing loud with his mouth open
2)in extreme anger when a person is out of control
3)in extreme sex and lust when a person is too much in state of lust
so when the person is we say a jinn possessed he see that creature some times and his body shakes or shivers and the entity has a control over him.
they can be of different religion and races and Satan are there in washrooms ,bathrooms,dirty places.
The above is the root meaning of the word Jinn. The existence of the Jinn is firmly established by the Qur’an and the authentic Sunnah and the consensus of the Scholars (Ijma’) It suffices to say that the word Jinn and its derivatives occur more than 29 times in the Qur’an. A related word "shaytan" and its plural "shaytana" together occur more than 80 times. In fact, there is an entire Surah called Surah Al-Jinn, which speaks in clear explicit terms about the Jinn.The reality, which we have to affirm, is that the Jinn live in an established world unseen to us. They eat and drink, and procreate. Similar to Humans, some are righteous while others are not.
The Jinn were created before the creation of mankind. Their origin is from fire. The Qur’an verified these facts in Surah Al-Hijr: