Why this line has error?

Why this line has error?

I am a beginner of making JASS script, so I always see other people script for learn. But when i use local Target = GetSpellTargetUnit(), a error occur when I save. It say need a handle or something. Why???

local type [b]variable_name[b/] = value
Meaning you would need:
local unit target = GetSpellTargetUnit()

In other words, you missed the handle type.

ayuh, you havent told wc3 what it can store in that variable.