I had to WIKI it yesterday--

Types of franchise tag

There are two types of franchise tag designations: the exclusive rights franchise tag, and non-exclusive rights franchise tag:

An "exclusive" franchise player must be offered a one-year contract for an amount no less than the average of the top five salaries at the player's position as of a date in April of the current year in which the tag will apply, or 120 percent of the player's previous year's salary, whichever is greater. Exclusive franchise players cannot negotiate with other teams.

A "non-exclusive" franchise player must be offered a one-year contract for an amount no less than the average of the top five salaries at the player's position in the previous year, or 120 percent of the player's previous year's salary, whichever is greater. A non-exclusive franchise player may negotiate with other NFL teams, but if he signs an offer sheet from another team, the original team has a right to match the terms of that offer, or if it does not match the offer and thus loses the player, is entitled to receive two first-round draft picks as compensation