This document discusses abstraction in C++. It defines abstraction as representing crucial features without including unnecessary details. There are two types of abstraction in C++ - data abstraction, which hides data information, and control abstraction, which hides implementation information. Abstract classes can be used to provide structure without implementation. The document provides an example program using an abstract class and discusses applications like increased reusability and security from hiding details. Potential downsides of abstraction are discussed, like reduced performance from extra handling of abstraction.