Free Software, Freeware, Shareware : What are those?

I am sure you constantly came across with those words above whenever you want to download softwares. But have you ever think about what does it mean? Here is what I got from wikipedia :

Free software or software libre or you know better as Freeware is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with minimal restrictions only to ensure that further recipients can also do these things.

Freeware is computer software that is available for use at no cost or for an optional fee. Freeware is often made available in a binary-only, proprietary form, thus making it distinct from free software. Proprietary freeware allows authors to contribute something for the benefit of the community, while at the same time allowing them to retain control of the source code, future direction of development and preserve its business potential.

Shareware is a marketing method for computer software in which the software can be obtained by a user, often by downloading from the Internet or on magazine cover-disks free of charge to try out a program before buying the full version of that program. If the "tryout" program is already the full version, it is available for a short amount of time, or it does not have updates, help, and other extras that buying the added programs has. Shareware has also been known as "try before you buy". A shareware program is accompanied by a request for payment, and the software's distribution license often requires such a payment.