If you've never installed an operating systems onto your computer (like a new version of Windows or macOS), then you might find it easiest to purchase a computer that already runs Linux. A complete list of vendors can be found at linuxpreloaded.com but here is an abbreviated list:
You don't need to buy a new computer just to get Linux. You can install it yourself, although if you're not a computer expert then you might want to get help from your local computer geek, or just read up on the process so you know what to expect.
Using a "Live" installer means that Linux can run on your computer without installing anything. It's a risk-free way to try and see for yourself what Linux is. A Live installer is free to download from any Linux distribution, and it's also what you need when you do decide to install.
When running live, your computer uses just a USB thumbdrive to work. Linux doesn't access the hard drive inside the computer. You can launch all of the default programs, edit documents, and browse the web, but you won't see your data because Live Linux isn't actually on your computer yet.
Because it's only designed as a trial mode and it's running off of a USB drive, Live Linux is slower to load and to run. If you proceed to install, the system is able to operate much faster, because it has access to your usual fast hard drive.
When you're ready to install, all you have to do is backup your personal data, and install Linux onto your computer. From there, the rest of this website can help you find your way around.
A good Linux to start with is Fedora Linux. It's designed by independent developers around the world, but serves as the basis for Red Hat Enterprise Linux (RHEL), the operating systems some of the world's largest data centers run.
Download an installer for free from the Fedora website.