Soul. Aatmaa is pure and never dies.

In Naarad Puraan, p 433, four types of Aatmaa are mentioned -
(1) Aatmaa - Soul,
(2) Antar-Aatmaa - Inner Conscious,
(3) Param-Aatmaa - Ultimate Soul or Bhagavaan, and
(4) Gyaan-Aatmaa.

Aatmaa has 13 characteristics -
It cannot be burnt, It cannot be wet, It cannot be dried, It cannot be devoured by any weapon, 
It is not the subject of Indriyaan, It has no Vikaar (it is unchangeable), It is immortal,

In Geetaa, 2/23-25, also Bhagavaan Krishn says to Arjun, telling the characteristics of the soul -
"Neither weapons can devoured this soul, nor fire can burn it, nor water can wet it, nor air can dry it. This soul is un-pierceable, un-burnable, un-dryable. It is undoubtedly omnipresent, immovable and immortal. This soul is not the subject of Indriyaan, not thinkable by mind, and is unchangeable; that is why, Hey Arjun, considering the soul like this, you should not lament for it."

Aatmaa :- A reflection of Poorn Brahm inside us and every earthly and divine body.

Pretaatmaa :- A body (those are not of this plane) that is given to us after our death due to our Karm. It is also called "Yaatana Shareer". A body that is given to us for tormenting in hell and on the earth. Dhundhukaaree in Bhaagvat Puraan is an example of this. There are many such Yaatanaa or Niyantrit Shareer, like Pishaach, Raakshas, Asur, Brahm Raakshas (Pret of a Braahman), Dankinee and many others.

Furthermore - Pretaatmaa is not the soul of the dead, it is the another body for the dead that is not earthly. There can be other good bodies too, like Dev Yoni, Pitri Yoni, Gandharv Yoni, Yaksh Yoni, Vidhyaadhar Yoni and many others. You can call them good "Ghosts" but the ghost word is not good for
them. Aatmaa also resides in these bodies but they are not Aatmaa. Aatmaa is independent of all. The Shuddh or pure reflection of God is Aatmaa, irrespective of any earthly and divine body. Even Devtaa are not Aatmaa - they are in Dev Yoni.