"Shareware is a marketing method for software, whereby a trial version is distributed in advance and without payment, as is common for proprietary software. Shareware software is typically obtained free of charge, either by downloading from the internet or on magazine cover-disks. A user tries out the program, and thus shareware has also been known as 'try before you buy', demoware, trialware and by many other names. A shareware program is accompanied by a request for payment, and the software's distribution license often requires such a payment. Payment is often required once a set period of time has elapsed after installation. The term shareware was coined by Bob Wallace to describe his word processor PC-Write in the mid-1980s."
http://en.wikipedia.org/wiki/ShareWare