At Ubuntu's heart is the Linux kernel. Ubuntu relies on the architecture of Linux to communicate with a computer's hardware so that software can do what it's supposed to do. Ubuntu commands follow the rules and procedures that hundreds of other Linux distros also use. But Ubuntu has its own style and list of features.
Ubuntu has a graphical user interface (GUI), making it similar to other popular operating systems like Windows, Mac OS and even smartphone systems like Android. The OS represents applications as icons or menu choices that you can select using keyboard commands or a mouse -- there's no need to learn a library of commands or terms. If you've used other operating systems that rely on a GUI, you can navigate through Ubuntu easily.
The operating system supports a wide variety of software. You'll find dozens of examples of productivity applications, media software and communications programs that run on Linux and, in turn, Ubuntu. Some of them are compatible with applications that run on other operating systems, such as Microsoft's Office suite.
In fact, Ubuntu will support software that's compatible for Linux. In the end, Ubuntu is just one attempt at leveraging the Linux operating system in a way that's easy and intuitive for the end user. Behind the scenes and at its very core, Ubuntu is Linux. It's just the outward shell that sets it apart from a basic Linux distribution.
If you're curious about Ubuntu, you can download it for free and give it a try without risk. You don't have to replace your current operating system. Who knows? You might find that you prefer Ubuntu's approach and your next machine might well be a Linux system.