What is Qubes OS?
"Qubes OS is a security-oriented operating system (OS). The OS is the software that runs all the other programs on a computer. Some examples of popular OSes are Microsoft Windows, Mac OS X, Android, and iOS. Qubes is free and open-source software (FOSS). This means that everyone is free to use, copy, and change the software in any way. It also means that the source code is openly available so others can contribute to and audit it." Ref. qubes-os.org
The QubesOs uses Virtual Machines to seperate your use of the computer.
One Virtual Machine can be setup to do work tasks, like browsing bank site a.s.o.
Another Virtual Machine can be setup to use Youtube.
The Virtual Machines are running seperate, so no data can be tranmitted another Virtual Machine.
For more info se video below.