Pretty much right there SH.
MAME is the standard stock version with operates from a command line.
MAME32 is exactly the same thing, but with a GUI grafted on the front that does all the legwork.
Hence with standard MAME you specify your options with and play the games using the ini file and by running it with the appropiate commands. With MAME32 you check boxes, select stuff from menus and double click on icons. Both are windows programs.
They are both the same program, built from the same source code, doing the same things. MAME32 0.61 does all the same stuff as MAME 0.61, just with a nice easy-to-use interface slapped onto it.