[JASS] explain handle?

im pretty familiar with JASS and the only thing i dont know how to use are the types 'Handle'.

ive seen several people use them in thier spells but cant figure out why.

so my question(s) is,
what is the type 'Handle'
why is it useful?
when should it be used?

and if someone can give an easy to understand example please.

All types except integer, real, boolean, string and code are handles.
For example:

local unit u = GetTriggerUnit()
local handle h = u // Legal: All units are handles
set u = h // Illegal: Not all handles are units

The advantage of handles is that any object can be referenced assigned to a handle.
It can be inverted with a function like this:

function HandleToUnit takes handle h returns unit
    return h
    return null
endfunction

function HandleToInt takes handle h returns integer
    return h
    return 0
endfunction

The HandleToInt function is great because you can get a unique integer representation for any object that way.

ok, im still not sure on its uses?

i mean, why do you want/NEED to use handle?

can you always get away without using them?

can u give an exmaple where something would be impossible to do without the use of handle.

You can completely avoid the type handle. It has no value by itself.
But on the other hand every unit, group, force, ... are actually handles since those types are derived from handle.
The only use I know of is using it with return bug functions so you do not need one for every type.

i dont know exactly but i think u can use handlevars to have them as "local vars" between several fuctions because "normal" local vars work in only one