If you've been following the long slog that is the Democratic primaries, chances are you'll have heard the phrase "Medicare for All" by now.

But what exactly is it, and would it really work in practice?

In the Last Week Tonight video above, John Oliver breaks all that down — and he has some strong words for the people who criticise it.

"I shit on Britain a lot on this show, and I'm not going to stop anytime soon. But one thing Britain does well is the National Health Service," Oliver says.

"I'll be honest with you, I've never had a bad experience, and I don't know anyone who has. But, since moving to America, I don't think I've met anyone who doesn't have at least one insurance industry horror story."

Oliver finishes by saying that he is personally in favor of some version of carefully designed, universal health care coverage.

"I will own all the things about it that are difficult, including the fact that politically, it would be incredibly hard to get passed," he says. "But in return, anyone who's resistant to significant change is going to have to own all the flaws of our current system.

"One in which, when Americans get sick, they can find themselves comparison shopping with a burst appendix, flipping a coin between life-saving medications, and praying they can come up with a catchy enough hashtag to cover their care."