The C++ Standard Library is a collection of pre-written code that provides essential functionalities for C++ programming. It includes various components such as data structures, algorithms, and input/output handling, which help developers write efficient and reliable programs without having to code everything from scratch. This library is organized into several parts, including the Standard Template Library (STL), which offers templates for common data structures like vectors and lists. By using the C++ Standard Library, programmers can save time and effort, allowing them to focus on the unique aspects of their applications.