Simple premise. A squad command that makes your squad take a couple steps in an outward direction, and place whatever mine is in their inventory.
Mines are extremely useful tools. However, it can be a pain having to switch through each of the squad-members to place each individual mine. Giving a squad order like this can speed up the process, at the cost of placing them more randomly. You still have the option to do it the normal way, but this is great to set up a quick minefield. Especially when you are going through squads rapidly.