It's a web site building tool, but the difference is that it's free (for up to 6 pages) and much more importantly, it's practically idiot proof. If you can use Word and know how to drag and drop, you can really create a brilliant website in a really short time. Here's the advertising video - I'm honestly not on any kind of commission for this, but I'm so impressed.
The first time I put a web site together it was really painful, so this is a joy. You can put your web page together and then try out different templates, too. For learners, you could use it for project work - they could make their own websites - I think this would be very motivating for teenagers, in particular, or you could make a class website and give each group in the class a page to complete. Alternatively, produce one yourself to give them practice in extensive reading or listening to authentic material - it's just as easy to edit as it is to set up. Have a go - if you thought websites were something that required a professional web designer and a lot of cash or a lot of time learning the ropes, think again - you CAN do this!