But what does open source actually mean?
Open source means open source software that is free of charge.
It is often the case that open source software can be used free of charge. But this would be a very reduced view of Open Source.
Open source means that the source code of a software is openly accessible and that it can be edited.
Yes, that is true – but not entirely. The open source code is only one criterion of open source.
Open source means much more than just software. Open Source is both a movement and a state of mind. The Open Source Definition contains a total of 10 criteria that describe the Open Source idea.
Just right! The Open Source Initiative names a total of 10 criteria by which open source can be recognised: https://opensource.org/docs/osd
The term “open” is explained very nicely in this 10min video: https://www.youtube.com/watch?v=9K-MG8LnXAk&feature=emb_logo