Cover 3 divides the deep field into three zones. Learn each defender's job, strengths, weaknesses, offensive answers and how to recognize it live.

Mesh pairs two shallow crossing routes to stress man and zone coverage. Learn the route spacing, quarterback reads, legal limits and defensive counters.

Illegal motion is a five-yard NFL penalty when an offensive player is moving illegally at the snap. Learn who may move, which directions are legal, and how the foul differs from an illegal shift or false start.

Roughing the kicker is a 15-yard penalty and automatic first down. Learn how it differs from running into the kicker and when contact is legal.

An illegal shift happens when multiple offensive players move before the snap and the offense fails to reset for one full second. Learn the five-yard NFL rule and how it differs from illegal motion and a false start.

An ineligible receiver downfield flag requires an ineligible player’s entire body to be more than one yard past the line before the pass. Learn the NFL rule and five-yard penalty.

A muffed punt happens when a returner touches the kick without gaining possession. Learn how a muff differs from a fumble, who may recover and why the kicking team cannot advance.

Down by contact ends an NFL play when opponent contact causes a runner to touch the ground with more than a hand or foot. Learn the exceptions and fumble rules.

Forward progress preserves the farthest point a ball carrier reaches before momentum stops. Learn how officials spot the ball, end the play and handle fumbles.

Prevent defense protects against a fast touchdown by keeping routes in front, trading selected short gains for time and protecting a late lead.

An NFL offense needs at least seven players on the line, eligible receivers on both ends and clear eligibility. Learn the five-yard illegal-formation rule.

Clipping is a 15-yard NFL foul for blocking a non-runner from behind and below the waist. Learn the four tests, exceptions and similar penalties.

An NFL blindside block is a 15-yard foul defined by the blocker’s path and forcible helmet, forearm, or shoulder contact. Learn the key exception.

A horse-collar tackle is a 15-yard NFL personal foul. Learn which collar and nameplate grabs count, the key exceptions, and how replay assistance works.

A facemask foul requires more than incidental contact. Learn the NFL grasp-and-control standard, 15-yard penalty, helmet-opening rule and replay limit.

Roughing the passer is a 15-yard penalty with an automatic first down. Learn the one-step window, protected contact areas and what changes outside the pocket.

A chop block is an illegal high-low double-team on the same defender. Learn the NFL definition, 15-yard penalty, reverse chops and the cut-block difference.

A cadence is the quarterback’s full pre-snap rhythm. Learn how snap counts, hard counts and silent counts keep the offense synchronized and test the defense.

A bootleg fakes a run one way and moves the quarterback outside the pocket the other way. Learn the routes, reads, naked bootleg and defensive counters.