@kdrafa91 "all the units packed as 1"
Do you mean all of the units swarm to a single point? That sounds like "split move"
If I select 20 tanks and give them a regular move order to some waypoint, each tank won't try to step on that 1 spot. They will each move to a spot such that the tanks end up in a formation around the waypoint.
When this happens, all 20 tanks share a single "move" order to that waypoint. And you can do things like hold shift to drag the waypoint somewhere else. Or ctrl-shift-right click to delete that waypoint. Since the order is shared by all of the units, deleting it once takes it away from all of them.
There are a few alternatives to this "regular" way of giving a move order.
If you select the units, put the cursor where you want them to go, hold down the right mouse button (RMB), you will see a ghostly formation appear. You can modify this formation by left-clicking and by moving your mouse. When you let go of the RMB, the units that you had selected will have a special kind of move order, a "formation move." They will try to organize themselves into a formation first and then they will try to travel to the waypoint in formation (traveling the entire way in formation, which can mean going only as fast as the slowest unit)
This is also a single order that is shared by all units. I would not describe this as "all the units packed as 1"
Another alternative to a regular move order is "split move." If you select 20 tanks, give a single move order, then (while the tanks are still selected) press "shift-g," the game will transform your single move order into 20 different move orders. Each of the 20 tanks will now have a single move order, and all them are to the exact same spot. If you want to modify these orders, any time you try to move or delete an order you will only move or delete 1 of the 20 orders.
This means they will all try to occupy the same space, so you can create a traffic jam and they will bunch up more densely than if you gave a normal move order. This density is important for a number of reasons. (1) it's much more vulnerable to area of effect weapons like bombers, overcharge, light arty; (2) more tanks in some small area = you have more DPS from that area (3) more density = harder for an ACU to walk around them, if you can confound an enemy ACU's pathfinding, it has a harder time escaping . . . I think this is what he means by "all the units packed as 1."
It is common to use shift-g to swarm an enemy ACU when you want to finish it off with tanks (normal doesn't mean "you should always use it" . . . you have to decide whether it is the right move in any situation).