Multifinder replaced Switcher to enable MacOsClassic to cooperatively multitask more than one application, including the Finder. Made Desk Accessories redundant as you could now have applications open at the same time. Worked quite well, although whilst background printing you could not do much in the foreground application. It was used in earlier versions of the mac os. It is now somewhat revived in mac os X 10.3 where you press "apple key" and Tab to switch applications.