What is Cygwin?
Cygwin tools are, in the words of the Cygwin homepage, “ports of the popular GNU development tools and utilities for Windows 95, 98, and NT. They function by using the Cygwin library which provides a UNIX-like API on top of the Win32 API.” Cygwin provides the compiler (gcc), libraries, headers, and other utilities which build and support the operation of Cygwin/X.