The C++ Standard Template Library (STL) is a powerful set of C++ template classes and functions that provide common data structures and algorithms. It includes components like vectors, lists, sets, and maps, which help manage collections of data efficiently. The STL allows developers to write more generic and reusable code, reducing the need for custom implementations. In addition to data structures, the STL offers a variety of algorithms for tasks such as sorting, searching, and manipulating data. These algorithms work seamlessly with the provided data structures, making it easier for programmers to implement complex functionalities without starting from scratch.