There are there 3 parts of Demon Possession & clearer examples of their differences;

1. Where the Demon merely manipulates the individual.

2. Where the Demon does favors, ( grant's wishes ), for the individual.

3. Full body possession. ( Full control ).

Poltergeist Spiriting can also be listed here because of their use of Objects to relay their messages. They have been known to be & do things both good & bad as well in humor - all depending on the entity itself. They have not been known to actually 'posses' an individual, but to feed off a persons energy.

EXAMPLES OF THEIR DIFFERENCES

-A Ghost will use an object/person to relate a message. ( Be it anger, happiness, etc. )

-A Demon will use/possess an object to cause harm to either the user or those around or in contact of said object or to entice the person they wish to possess.

-A Ghost will haunt a building, area, etc.

-A Demon will possess a person, object, or even an animal and control it's will to carry out their bidding. ( Accounts of these are found even in the Bible ).

-A Ghost will be attached to an object, place or area.

-A Demon will use/possess an object or person to carry out it's 'mission,' cause pain, etc. Demon possession of a  House; it takes it over, adds it's essence to it & virtually becomes the house.

-A Ghost will channel a message through a person. ( This can be done through visions, writings, dreams, etc. and is temporary )

-A Demon will possess a person - controlling them. ( Levitation, automatic writing also falls here, etc. & is indefinite )

Even though similar - see the difference?