Yes, it is. It's a website builder from Google that — like any other site builder — has its own strengths and weaknesses. But many (if not most) people don't use it because it's very limiting in design. First, there are very few design templates to pick from. But even the website templates available are barely customizable. There's no CSS or HTML editing access, so if you want to create custom functionalities, it's a no-go. And then there's one more major downside to it: you can't use a custom domain with Google Sites. If you're looking to build a business website, that's a big one — since any website with sites.google.com/[yoursitename] as its URL doesn't look as professional as most other professional websites.