What is a dummy unit?

What is a dummy unit? and how do i make one?
Lol I don't really care if that sounds noob, everyone finds out somewhere, somehow...

In general, a temporary unit that casts a spell or is part of an effect but isn't under player or AI control. Just a name-it gets no special treatment from wc3.

A dummy unit usualy has no visible model, no shadow, no attack, and has the locust ability which makes it unselectable and untargetable. It is used for casting spells outside of player's control; for example, let's say you want to make a spell that increases attack damage of allies and reduces attack damage of enemies in range of the caster: a combination of Roar and Howl of Terror. Obvously, your hero can only cast one of the two spells, while the second one has to be cast by a dummy caster that is created by a trigger when the hero casts the first spell. This way, the two spells appear to work as one.

You can also call the units that are used as projectiles by triggers dummy units. These units do have a model, but are equaly unselectable and untargetable, and are only in the game to make a graphical effect.

All in all, the term "dummy unit" is applied to units that the player doesn't control normaly, but are instead created and controled by triggers to achieve various effects.

So how does it work with no model? I mean what model do I give it to make it invisible?

Units - Zone Indicator (custom campaign), for example.

Yeah, but what MODEL do I use so it has none?

something invalid. for example type in as custom "none.mdl"

Kaldoreielf - "Units - Zone Indicator (custom campaign)" is a model file that will make the unit invisible. Please check all the model files available for the units :)

ok, now I place it on the map, and it shows a big green cube?

That big green cube will only show up in the world editor - in game, it will be a blank model.

ok thanks, so when using it in a trigger, I select the green cube?

For my dummy units, I just use a wisp with a scale factor of .01 and a selection scale as zero. That works, right?

Usualy, you don't preplace dummy casters, but create them dynamically as needed. When you need a spell cast, create the dummy caster, give it the spell, give it an expiration timer and order it to cast the spell.