A DOS cheating tool, residuing in your memory freezing or manipulating your memory content at will.
This quite popular little helper - commonly distributed, known (and used I guess) in it's shareware version, made our all lives a lot easier. Think of it (if you don't already know what this one is) as a program staying in the background, you press a hotkey, a neat menu comes up allowing you to edit your memory, search for several memory values (e.g. amount of lives left) and freeze them.
With this tool you could manipulate almost every game, if it was money, lives or even the copy protection (!) of some games. The shareware versions had some limitations (e.g. limiting the number of memory adresses to 10 per saved file, only searching onventional memory).