An abstract data type (ADT) is a mathematical model for data types, defined by its behavior from the point of view of a user of the data, specifically in terms of possible values and possible operations on data of this type. ADTs are a way of encapsulating data and operations on that data into a single unit, and they allow for interchangeable software modules. The definition of an ADT only mentions what operations are to be performed but not how these operations will be implemented. It does not specify how data will be organized in memory and what algorithms will be used for implementing the operations. It is called “abstract” because it gives an implementation-independent view.

Some key features of ADTs include:

• Abstraction: The user does not need to know the implementation of the data structure, only essentials are provided.
• Better Conceptualization: ADT gives us a better conceptualization of the real world.
• Robust: The program is robust and has the ability to catch errors.
• Modularity: ADTs can be combined with other ADTs to form larger, more complex data structures. This allows for greater flexibility and modularity in programming.

Examples of ADTs include lists, stacks, and queues. ADTs are a popular and important data type, and they are used to define or classify the type of values a variable can store in it.