An Abstract Data Type (ADT) is a high-level data structure that defines a set of operations and their behavior while abstracting away the implementation details. It provides a conceptual model for organizing and manipulating data in a modular and flexible manner.

The ADT specifies what operations are available and what their expected behavior is, but it does not dictate how those operations are implemented internally. This separation between the interface (operations) and the implementation allows for flexibility and modularity in software design.

ADTs are defined by their operations and their associated behavior.

Common ADTs include lists, stacks, queues, trees, graphs, and sets. For example, a stack ADT might define operations such as push (add an element to the top of the stack) and pop (remove and retrieve the top element), while a list ADT might define operations such as insert, delete, and search.

By encapsulating data and operations within an ADT, software developers can work with abstract concepts and focus on the logical design of algorithms without concerning themselves with the low-level implementation details. ADTs can be implemented in various programming languages using classes, structures, or other data structures provided by the language.

ADTs are often associated with Object-Oriented Programming (OOP) languages, as they provide a mechanism for defining classes and objects that represent abstract data types. However, ADTs can also be implemented in non-OOP languages using other techniques like structuring data with functions or using module systems.