Good, short description of the rules there. I played Wide Receiver for 2 years in the UK and followed the sport religiously for 20+ years so can also offer more details if anyone needs
Well you run or pass on offense and need to get 10 yards on 3 attempts to get another 3 attempts for the next 10 yards.And drive down the field to score by getting the ball in the endzone for 6 points,then kick the extra point or run and pass for 2 points.
On 4th down you punt the ball away,or kick a field goal for 3 points.Or even run and pass if it is short yardage in certain situations in the opponents half to keep the drive alive.
On defense you defend that pass or run.4-3 means 4 linemen and 3 linebackers,3-4 is the other way around.Nickel,dime,dollar are more to defend the pass as they bring in more defensive backs.
On defense you can blitz,bringing more guys at the Quarterback, play man coverage where defenders mark a set opponent player.Or zone,where a defender stays in an area until an opponent runs into it,then it is their reponsibilty to cover them.
I played strong safety in the UK for 5 seasons.So if you need to know anything in more detail just ask.
Yet to try the demo but definitely going to give it a go, hoping for a Vita demo too.