Its a league and union split.
union is played by solicitors, i think from what you have told me its the most like american football. The rules are the original rugby rules, more stops which (dependign on your point of view) either interupt the flow of the game, or build tension.
League is basically plyed by miners sons and young lads from wigan. (er go as a 'blue collar' sport will never get the backing) It has a more fluid game play, less stoping, more pauses as the rule system is simplified.
There are a lot of grass roots league teams, but the southerners and posh universitys play union as its 'old school' so league will never have a chance.
But basically league is what the miners sons and other scrotes play.
Football is playes by scousers, mancs, cockneys and other undesirables.
Tackling in both cases involves bringing the players armsholding the ball into contact with the ground, whilst the tacklers still maintains hold of him (so if he's tripped he can carry on, they have to stop him dead) when he' sbrought down he has to release the ball, or pass it back, if not then foul is called. In league 6 tackles in a row lead to the ball being given to the other side, this doesn't apply in union, it only stops if afoul i scaled, or the ball goes into touch.