What is the difference between the tools in msys and mingw

Hi, all

I use mingw+msys on Windows.
I find there are some tools in both msys and mingw, such as libtool,
autoconf, automake, xz, zlib etc..

This really confuses me. I do not know why there will be two versions.
What is the difference? Which one should I use?

I guess this also bothers some new users, so I bring up the problem
here.


------------------------------------------------------------------------------
Come build with us! The BlackBerry(R) Developer Conference in SF, CA
is the only developer event you need to attend this year. Jumpstart your
developing skills, take BlackBerry mobile applications to market and stay 
ahead of the curve. Join us from November 9 - 12, 2009. Register now!
http://p.sf.net/sfu/devconference