There are eight players on the field. On any play from scrimmage, two of these are specialists -- the quarterback and offensive specialist (usually a wide receiver) on offense, and two defensive specialists (usually cornerbacks) on defense. The other six players play offense and defense, with one substitution each per quarter.
Dropkicked field goals earn 4 points, as opposed to 3 for standard placed FGs; similarly, dropkicked extra points after touchdowns earn 2 points.
Being in an arena, the field is Astroturf, of course. The field is 28 yards wide and 50 yards long, with 8-yard deep endzones. If you multiply these distances out, you come to 198' x 84', designed specifically to fit inside a standard 200' x 85' hockey rink. The hockey dasherboards are left up, but covered by foam rubber padding. A player pushed against the boards is considered tackled.
The rules of the game were sketched out on the back of an envelope by James F. Foster in 1981 while attending an indoor soccer game.