Due to the AI and somewhat clunky/bulky nature of Warcraft 3 units, players have learned how to both surround units and also block units. Body blocking and surrounding units are 2 critical features one should learn as they improve in this game. This is certainly not something to worry about if you are picking up the game for the first time as hings like build orders and understanding how to creep are much more important. However, as you improve learning these 2 techniques will become imperative. Lets look at both of them separately.
Body blocking is exactly what it sounds like. You are using a unit (aka a body) to block another unit from moving in a way it would normally move. The basic idea is to get your unit in front of an enemy unit and then continuously block that unit from moving in a normal fashion forward. Normally you cannot fully stop a unit from moving (unless you get a surround which we will talk about next) but you can slow down a unit from how it would normally move. This can be used both offensively and defensively.
But first to better understand and visualize what body blocking is check out this iNSUPERABLE video in which he explains what body blocking is and how to do it.
It is important to note that there are numerous ways in which this feature can be crucial in a game. As I said before, it can be used both offensively and defensively.
Imagine if you will that you are running away several units including a weak 5 HP fiend. Furthermore, you are being chased by the enemies units which are naturally quicker than your fiend and you know you can save the fiend if you just get back to your close by base. You realize that the enemy will be able to kill your fiend before you get to your base. What can you do? In that case you may wish to use another healthier unit to “body block” the enemy units. You do this just like the video above described but instead of doing it for offensive reasons you are doing it to save your other unit. Just make sure you don’t end up losing your blocking unit just to save a weak unit. Although maybe you will sacrifice the “blocking” unit if you would rather lose that unit than your weak unit.
Conversely, body blocking can also be used to try and kill a unit or hero. This is described by iNSUPERABLE in the video above. Either way sometimes body blocking could result in winning you a game either defensively or offensively.
Surrounding a unit/hero/creep
Surrounding a unit/hero/creep can sometimes result in you winning a game or fight. But it is not something to get caught up on when you are learning as sometimes people concentrate so much on surrounding a unit that they forget they probably could have just killed the unit normally. Also since you usually need to use the “move” command (if you have not changed your hotkeys that would be the “M” hotkey for move) to execute a surround, you must pay specific attention in order to not end up just losing your army while moving after a unit and not attacking. Thus, this is definitely not something to get caught up as a beginner.
The basic idea is to position your units in such a manner around a unit/hero you want to surround so that you can then use the move command to surround it. This is done using the “move” command and not the attack command because if you press the attack command with melee or ranged units, there is the potential that a spot will be left open that the unit you want surrounded can slip out of.
iNSUPERABLE is well known for his ability to surround units and has done 2 videos thoroughly explaining how to execute a surround. Watch both of them and you will be well on your way to learning how to surround. He makes reference (and links in the youtube videos) a map you can use to practice your surrounds. I will also link that map below. You will not be able to execute surrounds easily right away. It definitely takes some time and practice to be able to execute surrounds comfortably and quickly with only a few units.
Here is the link to the map insup was referring to in his videos. https://www.epicwar.com/maps/97003/