Abstract Data Type(ADT) is a data type, where only behavior is defined but not implementation.
Opposite of ADT is Concrete Data Type (CDT), where it contains an implementation of ADT.
Examples:
Array, List, Map, Queue, Set, Stack, Table, Tree, and Vector are ADTs. Each of these ADTs has many implementations i.e. CDT. The container is a high-level ADT of above all ADTs.
Real life example:
book is Abstract (Telephone Book is an implementation)
