If you're a Windows user, your desktop environment probably isn't very far from this:
Pretty much all Windows users have the same desktop. You can still change your wallpaper, or the color of your windows decorations (default is blue), but basically you'll still end up with the usual Windows interface.
With Linux, choice has been brought back to you. You're no longer forced to accept the one-and-only way to manage multiple windows: you can choose among many programs, which are called "desktop environments". But don't worry, you won't need to worry about that, since you'll have a pretty good default. The point is you can change it if you wish.
So if you like a simple, efficient and easy-to-use desktop environment, you'll probably like this one:
If you like a more modern and glossy look, you might want to switch to this one:
Or you could try this one, simple and fast:
Or even this one, if you love to completely customize your desktop environment:
As you can see, with Linux you decide what your desktop looks like. And you don't even need to decide once and for all : you can switch to any of these desktop styles whenever you log into your computer.