A union consists of a number of elements that
A union consists of a number of elements that all occupy the same space in memory.
A union is a value that may have any of several representations or formats within the same position in memory; or it is a data structure that consists of a variable that may hold such a value. Some programming languages support special data types, called union types, to describe such values and variables.
A union is a special data type available in C that allows storing different data types in the same memory location. We can't use more than one member at a time. We can define a union with many members, but only one member can contain a value at any given time. Unions provide an efficient way of using the same memory location for multiple-purpose.