An American football field is a large, rectangular playing surface. The main field of play is 100 yards long, marked with a yard line every five yards. The numbers on the field count up from each end to the 50-yard line at the center.

This 100-yard stretch is often called the "gridiron" because of the pattern of parallel lines. The field is 53 1/3 yards wide. Between the main yard lines, you'll see shorter lines called hash marks, which indicate each individual yard. The ball is always placed on or between these hash marks at the start of a play.

At each end of the 100-yard field is a 10-yard area called the end zone. These are the scoring areas. To score a touchdown, a player must carry the ball into the opponent's end zone or catch a pass while inside it.

At the very back of each end zone stands a goalpost. It consists of a horizontal crossbar that is 10 feet off the ground, supported by a single post. Two vertical uprights extend upwards from each end of the crossbar. In the NFL, these uprights are 18 feet, 6 inches apart.

Goalposts are used for scoring by kicking the football. On special plays, a team can score a field goal or an extra point by kicking the ball through the uprights and over the crossbar.

Football is a high-contact sport, so players wear a lot of protective equipment. The most recognizable piece of gear is the helmet, which consists of a hard outer shell, thick padding, and a facemask to protect the face and jaw.

Underneath their jerseys, players wear hard plastic shoulder pads to protect their upper body during collisions. They also wear pads for their hips, thighs, and knees, which are inserted into pockets inside their pants. Players also wear cleats for traction and may use gloves to help them grip the ball.

The football itself is an oblong sphere, often called a prolate spheroid, which makes it easy to throw in a spiral. Officials also have specific equipment to manage the game. They use whistles to signal the start and end of plays and carry yellow penalty flags to throw when a rule is broken.

To track the ball's position, officials use a bean bag to mark specific spots on the field. To measure for a first down, a special sideline crew uses a 10-yard long chain connected to two poles. This device, often just called "the chains," provides a precise measurement to see if the offense has advanced the ball far enough.

Time to review what you've learned about the field and equipment.

Now, let's test your knowledge.

With a solid understanding of the field and the gear, you're ready to learn how the game is played.