The Standard Template Library (STL) is a multiplatform c++ library that allows for polymorphic data manipulation within data container classes. It eliminates the need to custom create linked lists, vectors, queues, and their associated sorting, insertion, and deletion routines. The programmer is freed from the need to re-write individual sorting, searching, and other mundane routines.
With the STL, a programmer can focus on the more unique and functional portions of their code.