The franchise tag is a single season deal, the terms of which are set by the NFL year on year. Specifically, they set the salary by position. Franchise tags are generally used to keep a player that doesn't have a long term deal worked out, or in a situation where the teams salary cap allowed for a short term deal but they didn't want to commit money where it wouldn't be effective.
Greg Hardy - Carolina Panthers
This is a typical case of a franchise tag, with Hardy coming off a great season and the Panthers not wanting to lose him. There is an expectation that they may come to an agreement over a longer term deal in the coming weeks, but the Panthers wanted to be assured Hardy for another year at the very least.Jimmy Graham - New Orleans Saints
This is a very similar situation, with the added complication of the wide receiver or tight end debate. Jimmy Graham wants to be thought of and paid accordingly, as a wide receiver. Anyone who has watched him play would rank his as a tight end who has the ability to play outside as a bonus to his game.Jimmy Graham is much like Hardy in the respect that this franchise tag is almost certainly just to tide the Saints over in case they can't reach a long term deal shortly.
Brian Orakpo - Washington Redskins
There never was a hope for a longer term deal in DC right now, but the Redskins didn't feel they could cut Orakpo loose as there isn't anyone else who could adequately fill his position in the team. This deal was coming a long way off, and is in place to give the Redskins more options going into 2015 - either through the draft, free agency or working out a long term deal with Orakpo.Nick Folk - New York Jets
Folk was already on a 1-year deal with the Jets, so moving to being franchise tagged isn't too much of a change with the exception of the extra $2.5+ million in salary. This move didn't make so much sense in my view, as kickers don't tend to be worth that kind of money, but the Jets haven't made a whole bunch of good decisions in recent years so it's not exactly a shock either.Transition Tags
A transition tag is often less desirable to use than a franchise tag as it allows a team to match any offer made under free agency by another team, this often results in peculiar clauses (such as getting bonuses based on playing in specific states, or playing against specific teams). These weighted deals present problems for the team tagging players as it makes it harder to keep a player, dependent on the interest in free agency.
Alex Mack - Cleveland Browns
Mack has been hit with the transition tag from the Browns. This gives them first rights to match any offer coming in for him. He's not a player they want to lose, but with the way some teams weight their offer sheets it could be all in vein.Jason Worilds - Pittsburgh Steelers
The Steelers may lose Worilds, but tagging him gives them the ability to match any offer sheet. This reads much more as a "we might as well tag him" deal than a real attempt to assure his future in Pittsburgh, only time will tell.