Privacy means being in control of ones own personal information. It does not mean secrecy but deciding on your own what you share and with whom and what you do not share.
On computers you can only have this control over your data when you have control over your computer. You should be the one deciding what your computer does, what software runs on its processor, what it does with your hardware and what it does with your data.

That is your personal freedom. Software should respect this freedom. That means you have to be in control of the software. This requires the following things:

• You should have the freedom to use the software for any purpose. Only you should decide and control what you do with your hardware and data.
• You should have the freedom to see what the software does. The software should be transparent and open source. To be in control of your data and your hardware, to be able to freely decide over it software should be open source so that you and anyone else who obtains a copy of it can freely check and see for themselves what the software does.
• You should be allowed to freely modify the software. To be in control of the software and in extent your device and data you need to have the right to modify the software to your liking: to remove any features that you dislike, that handle your hardware or data in a way you do not approve of, to modify features to your liking so that they suit your use case and use your hardware and data in the way you choose and to add new features so that you can do with your hardware and data what you choose to.
• You should be allowed to freely redistribute and publish the software and your modifications to it. You should not be forced to keep your copy of the software and your changes to it to yourself. Others should have the ability to profit of them as well if you want them to and you should have the ability to profit of the work and modifications of others if they want you to be able to. Your freedoms over your device are only effective if you can run the software developed and published by anyone. You should not need to develop all changes to the software yourself. Everyone including people who cannot develop software themselves should have freedom over their device and data and people developing and modifying software should have the freedom to collaborate and to build upon another. Innovation, peace, human culture and progress depend on people working together and building on the work of others.

Software that adheres to these freedoms is called free software. Free as in freedom.

You can only own a device if it runs free software.
You can only have privacy if your personal information is processed by free software.

This work is licensed under CC BY-SA 4.0. To view a copy of this license, visit https://creativecommons.org/licenses/by-sa/4.0/