Groupon is the daily deal websites that serves many major international markets, offering one coupon per day in each these markets. You can’t go anywhere online these days without spotting a Groupon ad. It's theory as we all know - the social features of its deep-discount offers for local merchants — a certain size group had to sign up in order for the deal to be “on” has been the reason for the huge success.
Free and open source software (F/OSS, FOSS) or free/libre/open source software (FLOSS) is software that is both free software and open source. It is liberally licensed to grant users the right to use, copy, study, change, and improve its design through the availability of its source code.