is simply restarting a play after some sort of infringement (knock on, offside or something like that). So in Rugby the idea of "advantage" is one that the ref will control so that other team that didn't infringe isn't taking advantage...so the ref will call a scrum.

So...let's talk about position in the scrum as maybe this can help...Think LOS in American football here...(PIGS if you will).

You have in Rugby, basically two "groupings" Forwards and backs. Forwards in Rugby would be somewhat considered your LOS or DL/OL. Backs in rugby would be your QB, RB, WR, TE (Jonah Lomu, Tongan) would be the ideal TE in Rugby, BIG, strong, fast and couldn't be stopped.

Anyhow, Forwards provide the scrum and I am reaching deep in my mind to name this properly.

You are a camera overhead looking down on the scrum, this is what you will see from your POV.

Left Prop (prop is that position to prop up the hooker, which is in the middle and then the right prop. That is 3 on your front line.
two locks to lock in the front line props and hooker...
Flanker on the left and flanker on the right, and the #8 behind both flankers...this position will kick the ball out to the scrum half (backers) or the flanker will. So from your POV, the positioning will appear as a 3, 4, 1.

That makes your SRUM in rugby. So you need big, quick and strong forwards and IF you have a team that can match that same size and strength with the element of a WR, RB then your backers will be DEADLY. Hence, BYU backers over the past few years (five) have been the best in Rugby...deadly, physical and quick. Cal couldn't counter with BYU backs.

Hope this helps...