It’s an operating system that originated as a clone of the ancient UNIX – much like Windows originated as MS-DOS. Linux is popular because the source code is licensed as free software (i.e. it’s in the cultural commons and free to be used and changed by anyone without fearing lawsuits). The fact that it’s free is why there are so many different operating systems built on top of it: Ubuntu, Fedora, etc. Linux is often used on servers, such as at Google, Microsoft, Amazon etc. However it’s also used on desktop PCs to a lesser extent. Because the source code is open to inspect, it’s considered more trustworthy than Windows/MacOS. This is also why https://www.privacytools.io/operating-systems/ recommends it.

https://www.pcworld.com/article/2918397/how-to-get-started-with-linux-a-beginners-guide.html Starting with a live USB from which you can boot Ubuntu is how I got started. A live USB allows you to use Ubuntu without having to install it to your hard drive. You can look up things you don’t understand using the pre-installed Firefox. ArchWiki and just looking stuff up on internet in general is how I slowly got to learn how to use GNU/Linux.

Specifically I recommend

1. downloading an ISO file from Ubuntu’s official website
2. using http://rufus.ie to copy that Ubuntu ISO onto a USB stick
3. rebooting your computer and figuring out how to boot from USB (this is different for each computer, use duckduckgo to look it up)

Alternatively you can use VirtualBox to mess around with a “virtual machine” (a fake computer inside of your computer) and install Ubuntu on there.