Well, it of course doesn't offer any real advantages over an actual computer (other than maybe size), but the price tag is so low that it reaches out to people who either don't have a home PC, or can't code on their main PC as they'd like to for whatever reasons. And that's without mentioning the applications it could have in schools. People who already have as much access to computers as they want aren't really the target market, although it's possible that something more oriented towards programming might push some people towards it, but that's besides the point. And sure, you need an input device as well as a TV, but that costs all of £10, so the whole setup remains about a third of the price of programmable calculators, which only tend to support BASIC and assembly anyway. And there'll presumably be some documentation, but the reason it has an ethernet input is so kids can look into more advanced materials etc. online.
It's just a cheap option, albeit one with various open-source packages for learning pre-installed.
It's not - it is a PC, just a very cheap one, that will come with various preinstalled packages (some learn to code for kids thing, then support for python, C and some other things if I remember correctly, with a focus on python). But yeah, it's a PC, so you can do whatever you want with it ultimately, although it of course has limited memory and specs. And Windows currently doesn't support ARM processors (although I think Windows 8 might?) so for now it'll all be Linux. Which is probably better to help people actually understand computers.