@Bobscrachy
It is a platform for migrating Unix applications to other PCs and you are not likely to learn much about Linux from it
Cygwin is a set of powerful tools to assist developers in migrating applications from UNIX®/Linux to the Microsoft® Windows®; platform. Cygwin delivers the open source standard Red Hat GNU gcc compiler and gdb debugger on Windows. In addition, it provides for a standard UNIX/Linux development environment on Windows including APIs and command shells. The Cygwin.dll library, included with Cygwin, delivers the interesting subset of UNIX SVR4, BSD, and POSIX APIs to enable quick ports of UNIX/Linux applications to the Windows platform.
What Can Cygwin Do?
With Cygwin, administrators can easily remote login to any PC, fix problems within a UNIX/Linux shell, on any Windows machine and run shell command scripts. Sophisticated shell command scripts can be created with standard shells, sed, awk, etc. Standard Windows command line tools can even be intermixed within the UNIX/Linux shell script environment to administer the Windows system. Over the years, UNIX/Linux system administrators have developed a large toolbox set of management scripts for their UNIX/Linux machines. Cygwin provides the ability to continue using these scripts on Windows machines.
Brian