What are variables!?

What are variables!?

I am always creating trigger maps. I also have now a campaign which consists of 12 maps. They're all without variables! I don't know them so could someone can tell about it?

you can assign nearly everything to variables, e.g. a special unit/hero you wanna transport from map to map. For example, you assign your hero to a variable called "MyHero" (the variable type has to be "unit"). Now, other triggers can refer to the unit by refering to it's variable, e.g. a trigger like <<Unit - Kill "MyHero">>

Extensive maps/campaigns can't be done without variables, e.g. transporting a hero from map to map is impossible without variables. ATM I'm writing a tutorial concerning to hero-transport, look it up when it's finished.

u need variables to refer to certain things. for example in a spell map: u have a unit casting a spell. if u would create triggers like this:

event: generic unit starts casting an ability 
action: wait 20 sec.
         set triggering units life to 200

this will not work correct, because after twenty sec. there isn't a "triggering unit". if u use a variable

event: generic unit starts casting an ability 
action: set"an unit variable"=triggering unit
         wait 20 sec.
         set "unit variable"'s life to 200

it will work

variables are e.g also important for rpg's, campaign's, td's and 99% of all maps u can find in the cusom game list in b.net

last, but not least i quote myself:

variables make making maps easier

Every map you make needs variables.

not melee maps and some 1 player rpg's

Well my Race Champion Wars does