Ask HN: How does this unicode url works?

[Warning those are spam links]

I've been receiving spam urls for a while but this one grabbed my attention:

непереводимая.рф

When I access it, it redirects to xn--80adgcaax6acohn6r.xn--p1ai

is xn--p1ai a valid TLD?

How come the browser accepts it as a url in the first place?