What is Right Of Possession?

Legal Definition
The right of possession (jura possessionis) means that someone currently holds something in hand and this person may be the temporary keeper or the long-term owner of an object.

This term is most commonly used in regards to property and is a land-backed asset. This legal tradition holds that whoever occupies property and uses it for its social function has the right to possess it.
-- Wikipedia
Legal Definition
The right to possession which may reside in one man, while another has the actual possession, being the right to enter and turn out such actual occupant; e. p., the right of a disseisee. An apparent right of possession is one which may be defeated by a better; an actual right of possession, one which wlll stand the test against all opponents. 2 Bl. Comm. 196.
-- Black's Law Dictionary