According to Wikipedia, "Freeware is software, most often proprietary, that is distributed at no monetary cost to the end user. [...] Unlike with free and open-source software, which are also often distributed free of charge, the source code for freeware is typically not made available." (src)
According to Wikipedia, "Free and open-source software (FOSS) is software that can be classified as both free software and open-source software. That is, anyone is freely licensed to use, copy, study, and change the software in any way, and the source code is openly shared so that people are encouraged to voluntarily improve the design of the software. This is in contrast to proprietary software, where the software is under restrictive copyright licensing and the source code is usually hidden from the users." (src)
You can check out Wikipedia's list of free and open source software packages!