League and Union are played differently due to different rules.
Rugby league has a 6 tackle rule. You get 5 tackles to advance from the moment your given side gains the ball. After the 5th tackle, the ball must be kicked away. Ideally, far enough that it will make the opposing team work to get up to the try zone. Rugby league is a fast game, and it's highly dependent on positioning.
Rugby Union has unlimited tackles. Scrums and rucks are also much more prevalent as since there are no tackle limits, speed is not so much of an issue. the game generally revolves a lot more around a brawl of a match through most of the center of play, slowly working your way up the field.
The main division is between north-south in the UK at least. Rugby league is very prevalent in the north of the UK, Rugby union much more so in the south.




