My understanding would be:

• Probabilities: Chance of a certain outcome happening. E.g. Outcome A has a 70% chance B a 20% and C 10%

• Possibilities: what outcome scenarios exist. E.g. there exist 3 (A B C). Those Possibilities might have a probability associated with them

• Plausibility: looks at the degree of truth of a statement. So if it logically makes sense and is the correct answer/is what happened. You might make a judgement of the plausibility of a possibility based on the probability of it happening. Say if something has two outcomes one with a 99% chance and the other 1% then that might be the more plausible one. Or if it has no chance, then it might be implausible

Edit: since someone mentioned the example of a coin toss.

Head and tails have a probability of 50% each (for the sake of simplicity I assume it won't land standing up)

A coin toss has two possible outcomes (possibilities). Head and tails.

Someone says he flipped a coin and got head 1000 times in a row. That's not plausible with a fair coin because of the low chance of it actually happening (even if there is a indefinitely small chance). As a result you might assume he is either lying or the coin is weighted for that outcome.