Short answers, pulled from the story.
A free agent is a player who is eligible to sign with any club or franchise without restriction. This status applies when contracts expire and allows athletes to negotiate with multiple teams.
The European Court of Justice issued a landmark decision on the 1st of March 1993 that changed association football forever. The Bosman ruling established the right of free agency for all players within EU member nations.
Unrestricted free agents are defined as players with four or more accrued seasons of service whose contracts have expired. These athletes can sign with any franchise without restriction.
Eight players sued the NFL claiming this arrangement violated antitrust laws. A jury found that Plan B was an unlawful restraint of trade in 1992.
Those who pass through several rounds without selection become unrestricted free agents known as undrafted free agents. The term is most common in the National Football League where rookies enter directly into the league.