The site estimates the likelihood of making the playoffs (including seed) and winning the Stanley Cup. It then looks at the nightly games, showing how the probabilities change with wins and losses of the teams playing.
It's a good resource, although it's been a bit messed up lately with how it's updating. When you click on conference right now, it's only updated up to last Friday even though the main page is only a day behind.
Users of the site should also keep in mind that the odds are dependent on the weighting of the importance of goal differential in a team's relative strength. The site tends to over-emphasize it sometimes to get more exciting swings in the odds. I do like though that it's taking into account strength of remaining schedule in its simulations.