Briefly on Linux and UNIX

UNIX is a proprietary (non-open-source) operating system developed by AT&T in the 1960s. Its advantage compared to existing OSes was that (1) it allowed several programs to run on the device at the same time, (2) allowed more than one user to access the system at the same time and, most prominently, (3) was able to run on various devices.

This 3rd trait is called portability, and the reason that UNIX excelled in it is that UNIX was written in the C language. Once a C source code is compiled on a machine, it is translated into the machine language that the device understands, so it can readily run on that machine.

In the 90s, Richard Stallman, a software programmer, wished to create a free, open-source OS similar to Linux. He started working on open-source programs he collectively named GNU, but couldn't devise a well-working kernel (heart of an operating system.) It was the Finnish software engineer Linus Torvald who coded a productive kernel he called Linux. Joining forces, the Linux operating system was released in 1991.

Follow-up question: According to the paragraph above, what is the source of the name "Linux"?