Qubes OS is a security-oriented operating system (OS). The OS is the software that runs all the other programs on a computer.
“A Reasonably Secure Operating System”
As name is Qubes OS, it states that this OS is not monolithic OS like others. It uses the concept compartments, which provide separate memory to execute every process with independent of each other. This is why it is Secure OS to use.
What is different with others OS?
Qube OS is based on different approach as compared to other OS. It consider security by compartmentalization methodology. It signifies that it will allow user work to compartmentalize the various parts of OS into securely isolated compartments and termed as QUBES.
In this manner, QUBE OS allows user to keep the different things on their computer securely separated from each other in separated isolated compartments called as qubes. Therefore, if somehow one qube had compromised; it will not affect the others compartments of machine i.e. if somehow user visited some malicious link in one qube and in another qube for doing online transaction. That malicious link executed malicious script and compromised your qube not system.
Hence, this compromised qube will compromise another qube in which user was performing online transaction. This attack will be limited to that qube only. All other qubes will remain unaffected. Same as in case of any malicious email attachments, because of compartmentalization, every attachment is open in its own single-use disposable qube.
This is how compart methodology as Qubes allows user to perform every activity on its single system without having afraid of successful cyberattack taking down your entire computer system (as zombie) in one go.
Together, all of these isolated qubes integrates into a single entity, called as OS. Every program allotted a separate isolated qube, but all windows are display in a single, unified system environment with comfortable GUI, which easily identifies windows from different security levels.