language agnostic - What is ADT? (Abstract Data Type)

Question

I am currently studying about Abstract Data Types (ADT's) but I don't get the concept at all. Can someone please explain to me what this actually is? Also what is collection, bag, and List ADT? in simple terms?

Answer 1

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)