Free software (also known as open source) is software that is owned by the consumer. These are also free to inspect, improve and adapt the software to their needs. And even share it with others, with or without their own changes. See the the page on free software from the Free Software Foundation Europe for more details.
This is in contrast to proprietary software, where the supplier owns the software, and gives you a restricted license to use it on their terms, and where only the supplier can improve or adapt the software.