A set is a well-defined collection of objects. Georg Cantor, the founder of set theory, gave the following definition of a "set" at the beginning. A set is a gathering together into a whole of definite, distinct objects of our perception and of our thought – which are called elements of the set.
The elements or members of a set can be anything: numbers, people, letters of the alphabet, other sets, and so on. Sets are conventionally denoted with capital letters. Sets A and B are equal if and only if they have precisely the same elements. A set is a well-defined collection of objects, whose elements are fixed and cannot vary. It means set doesn't change from person to person. A set may be denoted by placing its objects between a pair of curly braces. The objects in a set are called its members or elements or points.