Alternatively referred to as demoware or trial software, shareware is software that allows a user to try all or part of the program for free before buying it. It was a widely-used software distribution model in the 1990s, used by companies such as Apogee Software and Epic Megagames.
The idea behind shareware is that it allows you to try the program to make sure it is something you will find useful or enjoy. Users are encouraged to share the free version of the software, by copying it or downloading it from a BBS. If you enjoy the program, game, or utility and want more features, you can purchase the full version, or a key that will unlock the features.