The C++ Standard Template Library (STL) is a collection of pre-built classes and functions that simplifies and enhances C++ programming. It offers essential data structures, algorithms, and iterators, allowing developers to write efficient and reusable code. STL promotes generic programming, enabling solutions that work seamlessly with various data types. Its versatile algorithms handle tasks like sorting and searching, while containers manage data storage and manipulation. Iterators provide a consistent way to traverse and manipulate container elements. By abstracting complex low-level details, STL boosts productivity and code quality, making it a fundamental resource for modern C++ development.