Shareware is software that relies on the kindness of strangers to turn a profit. Downloaded from the Internet (versus sold in a store), it often has a free trial period (30 days or so) at which time the program stops working. Or it keeps on running, but your guilt (in theory) kicks in, prompting you to send the shareware developer a payment if you want to continue using it. Shareware, without fancy packaging or middleman, is usually ridiculously cheap - $10 or $20 - which is amazing considering it is often superior to store-bought goods (since you're downloading the latest, least-buggy release). An even better deal is freeware, which is, well, free.