Possibility is the condition of being possible. When something is possible it is within the limits of ability, capacity or realization; it can be conceived, take place or be done. When we say "possibilities" we can mean that something has potential value, as in "That Company has great possibilities".
With possibilities there are no assurances. Probabilities determine how likely and under what conditions possibilities can be realized. But probabilities are based on opinion, they are guesses and often the guesses are skewed by attitudes and beliefs. Probabilities can also be changed by changing the conditions that promote the possibilities.