Abstract data types (ADTs) are a way of encapsulating data and operations on that data into a single unit. They are a mathematical model for data types, defined by their 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. The definition of an ADT only mentions what operations are to be performed but not how these operations will be implemented. ADTs provide an implementation-independent view of data structures, allowing for greater flexibility and modularity in programming. 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: ADTs give us a better conceptualization of the real world.

• Robustness: 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.

ADTs are important in object-oriented programming and design by contract methodologies for software development. They allow for interchangeable software modules, as long as these modules share similar complexity behavior. Examples of ADTs include lists, stacks, and queues.