C++ is a middle-level programming language developed by Bjarne Stroustrup starting in 1979 at Bell Labs. C++ runs on a variety of platforms, such as Windows, Mac OS, and the various versions of UNIX. The C++ Standard Library is a collection of classes, functions, macros, constants etc which have been written in the core C++ language. There is a big list of required header files which can vary depending on different compiler implementations. This header list includes the headers containing the content from the C Standard Library, a list of new C++ specific headers, and other important headers for the C++ Standard Template Library (STL).
The C++ Standard Library is a reference for C++ programmer to help them at every steps of their projects related to system programming. All the C++ functions have been explained in easy to understand way and they can be used easily in your C++ projects.
A basic understanding of the C++ Programming languages will help you in understanding the C++ classes and built-in functions covered in this library.