Rugby debuted as an Olympic sport at the 1900 Paris Olympics, but was dropped as an Olympic sport after the 1924 Paris Olympic games. In 2016 at the Rio de Janeiro Games, a variation of the sport, rugby sevens, was reintroduced in competition. Here's what you need to know about the game.

How does rugby sevens work?

Rugby sevens is played with seven players on each side of the ball who compete for 14 minutes (two halves of seven minutes) with up to three matches a day, according to USA Rugby. In the Olympics, this format is followed for all matches except for the gold-medal match, which is 20 minutes long (two 10-minute halves), plus a three-minute halftime break. 

This version of rugby is faster and higher-scoring than the traditional version. Each team attempts to advance the ball into their opponent's area of the field (called a pitch) and touch it to the ground for a score worth five points (called a try).

Teams are only allowed to pass the ball backwards or sideways with no blocking allowed; using phases such as lineouts, mauls, rucks and scrums to retain possession (we'll get back to what those mean in a second). Kicking is the only way to move the ball forward. After each try (remember, that's 5 points), the scoring team is given an opportunity to kick the ball through the posts for an additional two points. Certain penalties also earn the non-offending team a kick through the posts, a penalty goal worth 3 points. However, penalty goals are rarely seen in sevens, according to USA Rugby.

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The team with the most points wins.

Can rugby end in a tie?

Yes and no. Typically, if both teams are tied at the end of regulation time, a 5-minute overtime knockout round will be played, where the first team to score wins.

In Olympic rugby, there is a round of pool play, like soccer's group play, with 12 teams divided into three pools of four. Teams in each pool play each other once, for a total of three games. Wins are worth 3 points, draws 2 points and losses 1 point, creating a ranking at the end of pool play.

The top two teams in each pool advance to the knockout stage, along with the best two third-place finishers.

If teams are tied in points, the result of the head-to-head matchup is the first tiebreaker. If the teams did not meet in a match, or if the match ended in a tie, aggregate points margin is used.

Who are the top Team USA athletes in rugby sevens?

Marcus Tupuola

Tupuola made his national team debut in 2019. He has 27 caps.

Alev Kelter

Kelter is a multi-time Olympian having also competed in the 2016 and 2020 Olympics. She was the number one scorer for Team USA in 2016 Olympics.

Rugby sevens positions

NBCOlympics.com has a great guide to positions and scoring, providing descriptions of each of the seven roles on the field. Here is what they say:

• Loose-head prop: The left-most of three forwards in a scrum. On offense, expected to gain tough meters with power and strength, breaking tackles. On defense, expected to hold a firm front line in the center of play. 
• Hooker: The middle of three forwards in a scrum. Uses one leg to “hook” the ball backward to his scrum half. Similar offensive and defensive roles as the loose-head prop. 
• Tight-head prop: The right-most of three forwards in a scrum. Similar offensive and defensive roles as the other forwards. 
• Scrum half: The player who feeds the ball into the scrum, then retrieves it to start and attack. On offense, transitions play between the forwards and the backline. On defense, provides an organizing role and often covers gaps between the forwards. 
• Fly half: Often the first person to receive a pass from the scrum half after a scrum. On offense, acts as the playmaker, finding space and springing breakaways through creative passing. On defense, covers the middle of the pitch, forcing the opposing attack out wide. 
• Center: The second-widest-playing member of the backline, between the center and the wing. On offense, combines playmaking ability with speed and elusiveness, scoring often. On defense, helps the center cover the middle of the pitch and stop opposing breakaways. 
• Wing: The outermost player on the backline. On offense, the most dynamic try-scoring threat, capable of long breakaway runs at any moment using speed and elusiveness. On defense, expected to chase down opposing breakaways and make try-saving tackles. 

Note: There are 12 players on a team, seven on the field and five on the bench. And each team is allowed five substitutions per game. Players can exit and re-enter the game, but each exit is considered a substitution.

Rugby dictionary of common terms, provided by USA Rugby

• Try | The main objective of the game, to touch the ball down in the opponent's in-goal area (tryzone) for a score worth five points. Unlike American football, the ball must be touched to the ground for the points to be awarded. Tries are the origin of touchdowns in American football. 
• Tryzone | The in-goal area where tries are scored. 
• Conversion | A kick worth an additional two points offered to the scoring team immediately after a try. Conversions must be kicked in line with where a try was scored. In rugby sevens, players may not place the ball on a tee and must kick the conversion using a drop-kick (tossing the ball above the feet and kicking it before it hits the ground).
• Penalty | A kick worth three points awarded to a non-offending team when their opposition commits a penalty. 

• Touchline (similar to sideline) | When the ball moves out of bounds or outside the field of play. 

• Tryline | The goal line the separates the area where a try may be scored and the remaining field of play 
• Tackle | A tackle occurs when the ball carrier is brought to the ground and held by one or more opponents. A ball carrier must release the ball immediately following the tackle. Unlike American football, play does not stop when tackles are made. 
• Ruck | A ruck is when the ball is on the ground and at least one player from each team closes around it while on their feet. The ball cannot be handled in the ruck, players must move it until it reaches a teammate's hindmost foot and can be picked up. 
• Maul | When the ball carrier is held by one or more opponents and one or more of his or her teammates bind on as well. The ball must be off the ground, a minimum of three players must be involved. 
• Lineout | A means of restarting play after the ball falls out of the field of play (touchline). Forwards assemble in a line on each side where one team's hooker throws the ball straight in the middle. Each team uses various formations to lift players up, retrieve the ball and put it back in play. Which team's hooker throws the ball into the lineout is circumstantial. 
• Scrum | A means of restarting play after an infringement. Each team's forwards bind together and connect with an opposing team's forwards. The ball is thrown into the middle of the tunnel by the non-offending team's scrumhalf. Both team's hookers use their feet to try and move the ball while also pushing the other team backwards until the ball reaches the hindmost leg of one of their teammates where they can claim possession. 
• Sin Bin | when a player is removed from the game and forced to sit out for 10 minutes (rugby fifteens) or two minutes (rugby sevens) for dangerous play or serious infringements.