MinGW refers to a set of runtime headers, used in building a compiler system based on the GNU GCC and binutils projects. It compiles and links code to be run on Win32 platforms... providing C, C++ and Fortran compilers plus other related tools. If you see references to "mingw32" instead of "MinGW", they are referring to the same compiler system. The project's name changed from mingw32 to MinGW is to prevent the implication that MinGW will only works on 32 bit systems (as 64 and higher bit machines become more common, MinGW will evolve to work with them). MinGW uses the Microsoft runtime libraries, distributed with the Windows operating system. Unlike other ports of GCC to Windows, the runtime libraries are not distributed using Gnu's General Public License (GPL). You, therefore, do not have to distribute your source code with your programs unless, of course, you use a GPL library in your programs.
Initially, MinGW was an assortment of individual packages... the MinGW runtime, various applications built using that runtime (gcc, ld, etc.), and other useful components (the w32api headers needed to code for the Win32 API). Developers "rolled their own" MinGW environments by downloading the latest versions of each individual package needed. This was necessary given the dynamic nature of early package versions (updates being posted constantly)... but was oftentimes confusing for newbies, and made it difficult for application/library vendors to design products that build with a "standard" MinGW environment.
Therefore, around mid-2001 when development had matured and updates were not being packaged as rapidly, the decision was made to create a single-file distribution of the standard MinGW environment. This single archive contains the files from each component package, bundled and ready to extract. The individual component packages are still available for download... if a particular package is updated in between releases of the overall distribution, it's possible to simply drop the newer package in place over a distribution install.
Packages included in MinGW
- mingw-utils - Miscellaneous utilities