Set: A set is a well-defined collection of distinct objects, which can be numbers, symbols, or any other items.
Subset: A subset is a set that is contained within a larger set, where all the elements of the smaller set are also elements of the larger set.
Union and Intersection: The union of two sets is the set of all elements that belong to either or both of the sets, while the intersection is the set of all elements that belong to both sets.