C++ is a superset of C that can run most C code while securing data through encapsulation. It uses both procedural and object-oriented programming, with an emphasis on data objects rather than just algorithms. Streams in C++ control the flow of data using classes and provide input/output operations by deriving from the base ios class. Different stream classes represent different types of data flow, with input streams reading external data into a program and output streams writing data from a program to an external location.