There are two types of data, namely, atomic and structured (also called composite) data.
Atomic data are data that we choose to consider as a single, non-decomposable entity. Boolean or logical data are examples. The integer 4562 may be considered as a single integer value. We can decompose it into single digits (4,5,6,2) but decomposed digits will not have the same characteristics of the original integer.
An Atomic Data Type is a set of atomic data with identical properties. These properties distinguish one atomic data type from another. Atomic data types are defined by a domain or set of values and a set of operations that act on the values. These are data types that are defined without imposing any structure on their values.