If you're unfamiliar with DVOA, it measures a team's efficiency by comparing success on every single play to a league average based on situation and opponent. Here's a short explanation:
DVOA measures not just yardage, but yardage towards a first down: Five yards on third-and-4 are worth more than five yards on first-and-10 and much more than five yards on third-and-12. Red zone plays are worth more than other plays. Performance is also adjusted for the quality of the opponent.
Not all three-yard gains are created equally. Neither are 28-yard touchdowns. Football Outsiders attempts to differentiate each play.