Shareware is software sold on a trial basis; you can use it for free initially, but must pay for it after a time. The package might require a password after a given period of time or number of uses, which you would receive after payment; or the free version might have reduced features. It's called 'shareware' because you can share the free version with anyone you like -- as long as you don't charge for it. One important point to note is that shareware is not necessarily of poor quality just because it is not sold in the usual way.