What's the difference between team pursuit, long-track, mass start, and short-track speed skating?
Traditional, long-track speed skating takes place on a 400 meter ice track, with skaters racing counter-clockwise around an oval for a set number of meters (between 500 meters and 10,000 meters). In individual races, pairs of skaters face off against one another on the track at a time, one person in each lane, competing to complete the designated distance in the fastest time of all competitors (not just the person they're matched up against at the moment).
Team pursuit speed skating events also takes place on a 400 meter course, but involves two teams of three racing against one another. Teams start on opposite sides of the oval, and in order to win, all three team members must all cross the finish line before all three skaters on the other team (simple enough, right?). These races are single elimination, meaning the only way to advance to the semifinals or finals is to beat whatever team you're up against.
Mass start speed skating is a bit more involved, where up to 24 skaters face off against one another on the track at the same time, racing for 6,400 meters and doing intermittent sprint laps to earn extra points. It's arguably the most exciting of any of the speed skating events, and this is the first Winter Olympics it's appearing in, so it's definitely worth checking out.
Short-track is quite a bit different than the rest, taking place on a -- you guessed it -- shorter track. Specifically, the oval ice track is roughly a quarter the size of the long-track one at 111.12 meters. In short-track, between four and six skaters face off against one another simultaneously, and race to beat each other across the finish line after a designated number of laps (rather than long-track's time trials). Short-track is also the speedier and more crash-prone of the two, and skaters can hit up to 3Gs as they go around corners, or roughly what astronauts feel during liftoff.