The Standard Template Library, or 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 programmers manage collections of data efficiently. The STL is designed to be flexible and reusable, allowing developers to focus on solving problems rather than implementing basic data structures from scratch. 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, promoting code efficiency and clarity. By using the STL, developers can write more concise and maintainable code, enhancing productivity in C++ programming.