Alternatively called free software, freeware is software that is 100% free as long as it remains unmodified. The complete opposite of freeware is commercial software. Unlike open-source software, freeware cannot be modified and is often only licensed to be used by non-commercial users.
Freeware is often also donationware and if it's something you use, we strongly recommend donating to the author.
The term "free software" may also describe FOSS (free and open-source software). In this context, "free" means freedom and not free of charge.