Two teams play, with eleven players from each on the field at a time. A game is 60 minutes of playing time, split into four quarters of 15 minutes, with a halftime break after the second quarter. The field is 100 yards long between the goal lines, with an end zone at each end. The team with the ball is the offence and tries to move it toward the opponent's end zone; the other team is the defence and tries to stop it.

Football is played in downs, which are single attempts to move the ball. The offence gets four downs to advance at least 10 yards. If it manages that, it earns a fresh set of four downs, called a first down. If it fails after the fourth down, the ball goes to the other team where it stands. That is why teams usually punt (kick the ball away) or try a field goal on fourth down, although sometimes they "go for it" and keep the ball in their own hands.

La possession peut aussi changer via une perte de balle : une interception (une passe attrapée par un défenseur) ou un fumble (le porteur du ballon perd le contrôle et l'autre équipe le récupère). Une seule passe vers l'avant est autorisée à chaque jeu, et elle doit être lancée de derrière la ligne de scrimmage. Les remises de balle, les courses et les passes latérales ou vers l'arrière n'ont pas cette limite.

A touchdown is worth six points and is scored by carrying or catching the ball in the opponent's end zone. The scoring team then chooses between a one-point kick, the extra point, and a two-point conversion, a single run or pass play from close to the goal line. A field goal, kicked between the uprights, is worth three points. A safety, worth two points to the defence, happens when the offence is tackled in its own end zone. These building blocks explain why teams so often score in chunks of three and seven.

When a rule is broken, an official throws a yellow flag. Common fouls include a false start (an offensive player moving before the snap), offside (a player lined up beyond the line before the snap), holding and pass interference. Most penalties cost the offending team yards, often 5, 10 or 15, and some also hand the other side an automatic first down. The team that was fouled can usually decline a penalty if the result of the play was better for it.

Clock management is a big part of the strategy. The clock stops after an incomplete pass, when a player goes out of bounds, on a timeout and after most scores, but it keeps running after an in-bounds tackle. A team protecting a lead runs the ball to burn time, while a team that is behind throws toward the sidelines and spends its timeouts. There is also an automatic stoppage, the two-minute warning, near the end of each half.

The league is split into two conferences, the American Football Conference (AFC) and the National Football Conference (NFC). Each conference has four divisions of four teams, named East, North, South and West. In the regular season teams do not play everyone: a set formula gives each team more games against its own division and conference than against the other conference. The number of games has changed over the decades, and each team gets a bye, a week without a game, somewhere in the schedule.

If a game is level after four quarters, an overtime period is played. Overtime rules have been revised several times, including who is guaranteed a possession, and they have at times differed between the regular season and the playoffs. A regular-season game that is still level when overtime ends can finish as a tie, which is why N4's standings have a T column next to W and L. Playoff games continue until one team is ahead.

The playoffs are single elimination: lose and you are out. Each conference sends its division winners plus wild-card teams, which are the best records among the rest, and seeding rewards better records with home games and, in some formats, a first-round bye. The number of playoff teams has changed over time. The AFC and NFC champions meet in the Super Bowl, the title game, played at a venue chosen in advance. Tie-breakers such as head-to-head results and division record separate teams with the same record.

Each team has three units. The offence is led by the quarterback (QB), who throws or hands off the ball; running backs (RB), wide receivers (WR) and tight ends (TE) carry and catch it; and an offensive line, usually five players, blocks for them. The defence has linemen who rush the passer, linebackers (LB) who tackle and cover, and defensive backs, cornerbacks (CB) and safeties (S), who defend the pass. Special teams handle kickoffs, punts and kicks, led by the kicker (K) and punter (P).

Each position is judged on different numbers. A quarterback is measured by passing yards, touchdowns and interceptions, a receiver by catches, yards and touchdowns, and a defender by tackles, sacks and interceptions. N4's player cards pick their headline numbers by position for that reason. Offensive linemen rarely have counting stats, so team numbers such as rushing yards and sacks allowed tell you more about them.

A box score summarises one game. The line score shows the points in each quarter and in overtime, and the team stats typically cover first downs, total yards, passing and rushing yards, turnovers, penalties and time of possession. Player leaders name the top passers, rushers and receivers. Turnovers often explain results the scoreboard alone cannot, because a team can gain more yards than its opponent and still lose if it gives the ball away.

Schedules, live scores, scoring plays, team statistics, standings, rosters and player statistics come from the connected sports data provider, API-Sports. The hub shows the week's games, the next kickoffs in Eastern Time and a quick look at every division. Live games refresh roughly every 30 seconds, while standings and team pages are refreshed less often, so a table can lag behind a game that has only just finished.

Open any game to reach its N4 Game Centre. It shows the score by quarter, a timeline of the scoring plays, a team box score, impact leaders drawn from the game's player statistics, the current injury report where the provider has one, each team's division standing and their recent meetings. N4 shows only what the provider returns: when a figure is missing you will see a dash or an empty panel, not a guess.

La page du classement regroupe les équipes par division et affiche victoires, défaites, nuls, différentiel de points (DIFF), la série en cours (STRK) et les bilans à domicile et à l'extérieur. Le différentiel de points correspond aux points marqués moins les points encaissés, un indicateur rapide de la force au-delà du bilan victoires-défaites. Le N4 Power Board du hub classe les équipes selon ce différentiel. C'est une vue simple construite à partir du classement, pas un power ranking officiel.