In Nordic Skiing, there are multiple different race formats and distances.
Individual or Interval Start
1 to 5 skiers start at once with a 30 sec break in between each set. This is one of the most common race format for races. The distance is usually a 5k. Skiers race against the clock and the winner is the skier with the lowest time.
Mass Start
All of the skiers are lined up in rows and everyone starts at once. This can be a more challenging format because people can get tangled up with equipment in the first couple meters. The first athlete across the finish line wins.
Sprint
An official sprint event is usually 1-2k long and will consist of a qualification round, and then based on those results, skiers will be placed in heats of 4-6 in the quarter-finals with the top two from there advancing to the semi-finals. The top two skiers from the semi-finals advance to the finals. From the A finals the winner is declared.
Pursuit
This format is used for the Conference meet, Section meet and State meet. A pursuit consists of two races one skate and one classic. The first race is an individual start race where results are recorded as time back from the first place finisher. The second race uses the other ski technique and is started based on time back from the first place finisher. Here you try to catch the people in front of you in order to move up places in the race. The winner is the individual with the lowest combined time over the two races, which will be the person who comes in first on race two.
Continuous Pursuit
At the halfway point of the race, athletes enter the stadium and change skis and poles as quickly as possible. The first skier over the finish line wins.
Relay
Skiers work in teams of 3-4 and similar to a track relay have to "pass the baton" within an exchange zone. There is no real baton, hard to hang onto with the poles, but they have to tag their teammate for an official exchange. There will typically be two classic legs and two skate legs.