Operating system role

The role of an operating system is to provide a bridge between the computer hardware and the software applications that run on it.

The role for software developers

It provides lots of abstractions so that the software developers don’t have to worry about the low-level details of the hardware.

For example, instead of having to directly manage the CPU, memory, storage devices, and peripherals, the operating system provides a set of APIs and services that the software can use to interact with the hardware in a more convenient way.

You can think of the operating system as a kind of middleman that sits between the hardware and the software, managing resources and providing an interface for the software to use.

The role for end-users

You probably think of your operating system as the thing that provides the user interface to your computer - the desktop environment, the file manager, the taskbar, and so on.

It’s not really clearly defined where the operating system ends and the application software begins, since many operating systems come with a whole suite of applications pre-installed (like web browsers, file explorers, media players, and so on).

For example, ‘Linux’ itself is just an operating system kernel. If you used raw Linux without a distro, you’d just be using a kernel with everything else as extra, application software.
But most people run a distribution of Linux (like Ubuntu, Fedora, Arch, and so on) which bundles the Linux kernel with a whole bunch of other software to make it usable. The entire package is often referred to as an ‘operating system’ - whether the kernel itself is also an operating system is up to you to decide :)

In short, the operating system also usually provides the user interface and basic applications that users interact with on their computers, all as part of an ‘operating system package’.