STL stand for (Standard Template Library) and it is software library which extends C++ standard library's capabilities and provides a ready made set of common classes, including associative arrays and containers these are used along with built-in and user-defined types that support elementary operations. An STL includes sequence and associative containers and these sequence containers include deque, vector and list. The STL achieves its results through the use of templates and also provides compile-time polymorphism that is often more efficient than traditional run-time polymorphism.