The Standard Template Library (STL) is a set of C++ template classes to provide common programming data structures and functions such as lists, stacks, arrays, etc. It is a library of container classes, algorithms, and iterators. It is a generalized library and so, its components are parameterized. Working knowledge of template classes is a prerequisite for working with STL.
STL has 4 components:
Algorithms
Containers
Functions
Iterators
A Sample Video for C++ STL : https://www.geeksforgeeks.org/the-c-standard-template-library-stl/