First and second down from a team's own 20 to the opponent's 21, where most of a game is played.
Every number covers the games the filters select, and "field" is the other 67 elite teams in the same situation. Success is the standard rule: half the yards needed on 1st down, 70% on 2nd, all of them on 3rd and 4th. Dropbacks count as passes, so sacks and scrambles are included.