NFL free agency explained from salary cap and tampering to franchise and transition tags

The NFL’s free agency frenzy kicks off today with a 52-hour legal tampering period ahead of the official start of the new league year on Wednesday.

Several star players, including Vikings quarterback Kirk Cousins and Giants running back Saquon Barkley, will be free to sign a contract with a new team.

Here’s an explanation of rules and terms:

What does legal tampering mean?

At 12 p.m. EDT today, teams can start negotiating with players who will become unrestricted free agents when their contracts expire at the start of the new league year on 4 p.m. EDT on Wednesday. Players can’t sign with new teams until the league year officially begins. The two-day negotiating period applies only to players who will be unrestricted free agents.

Who are unrestricted free agents?

Any player with four or more accrued seasons — six or more regular-season games on a club’s active/inactive, reserve/injured or reserve/physically unable to perform lists — whose contract has expired becomes an unrestricted free agent and may negotiate and sign with any team.

Who are restricted free agents?

Restricted free agents are players with three accrued seasons who have received a qualifying offer when their current deals expire on Wednesday.

What is a franchise tag?

Each team can designate one potential free agent a franchise player. Eight players received the tag.

An exclusive franchise player is not free to sign with another club and is offered the greater of the average of the top five salaries at the player’s position for the current year as of the end of the restricted free agent signing period on April 19; or the amount of the required tender for a non-exclusive franchise player.

A non-exclusive franchise player can sign with another team, but that club will owe his previous team two first-round draft picks. All the players tagged this year are non-exclusive.

The time frame to sign franchise players is March 13 until Nov. 12.

What is a transition tag?

The transition tag is a one-year offer for the average of top 10 salaries at the position. It guarantees the original club the right of first refusal to match any offer the player might receive from another team.

The tagging team is awarded no compensation if it chooses not to match a deal. The time frame to sign transition players is from March 13 until July 22.

Only one player — Patriots safety Kyle Dugger — received the transition tag this year.

Teams can decide to withdraw franchise and transition tags and the player automatically becomes an unrestricted free agent.