A probability space is a mathematical construct that represents a random experiment or system in the world. It defines the possible outcomes, the possible collections of outcomes (events), and the probability that each of those collections of outcomes happen. Therefore, it is like an enumeration of everything that could happen, together with how feasible it is to happen.
Formally, a probability space is a tuple
NOTE that sample space, measurable space and probability space are increasingly larger constructs:
Sample space < Measurable space < Probability space.