a try is worth 4 points
after you score a try, you kick the ball off of a kicking tee 20 or so metres away from where you scored over the tryline. if you kick the ball between the post you get another 2 points.
if you are running with the ball and dropkick it between the posts you get 1 point.
now, if you score a try and someone on the other team, for example, comes up and deliberatly shuves you over, you get the 4 points for the try, than you attempt to kick the ball over the posts for another 2 points and then you get another kick right in front of the posts for an attempt at another 2 points. in total, that's 8 points. it's called a penalty try or 8 point try.
BTW, a try is a touch-down, only you don't trow it down on the ground, you have to place it on the ground without dropping it.