NFL Free Agent Types

"Unrestricted Free Agent" (UFA)
"[a] player [that] shall be completely free to negotiate and sign a Player Contract with any Club, and any Club shall be completely free to negotiate and sign a Player Contract with such player, without penalty or restriction, including, but not limited to, Draft Choice Compensation between Clubs or First Refusal Rights of any kind." Basically, what that means is that an UFA is free to sign with the highest bidder (or the team of their choice) without that team having to give the original team any kind of compensation. When a player with five or more accrued seasons (or with four or more accrued seasons in any Capped Year) reaches the end of his player contract, he becomes an UFA.

"Restricted Free Agent" (RFA)
"any Veteran player with three or more accrued seasons, but less than five accrued seasons (or less than four accrued seasons in any capped year)... At the expiration of his last Player Contract during such period... [the player] shall be completely free to negotiate and sign a Player Contract with any club, and any club shall be completely free to negotiate and sign a Player Contract with any such player, subject to... certain restrictions." The restrictions are the fun part.
 

• 2013 First Refusal Right Tender: $1.323 million
  This is the minimum tender a team must offer it's restricted free agent to "lock in his restriction".
  
  If a new team makes this same offer, or 110% of the player's previous year salary (if greater), the original team has the choice to match the offer. If they choose not to, the player can sign with the new team for $1.323 million, and the original team will receive the new team's draft pick in the round the player was originally drafted the following year. 
  
   
• 2013 2nd Round Tender: $2.02 million
  If a new team makes this offer, or 110% of the player's previous year salary (if greater), the original team has the choice to match the offer. If they choose not to, the player can sign with the new team for $2.02 million, and the original team will receive the new team's 2nd round draft pick the following year.
   

• 2012 1st Round Tender: $2.879 million
  If a new team makes this offer, or 110% of the player's previous year salary (if greater), the original team has the choice to match the offer. If they choose not to, the player can sign with the new team for $2.879 million, and the original team will receive the new team's 1st AND 3rd round draft picks the following year.
  
  In the event a Prior Club withdraws its Qualifying Offer, the RFA immediately becomes an UFA.

"Exclusive Restricted Free Agent" (ERFA)
This player has no more than two accrued seasons in the NFL and may only sign with his prior team, provided, of course, that the team extends a minimum qualifying offer to the player.