Spells script dúvida

local combat = createCombatObject()


   setCombatParam(combat, COMBAT_PARAM_TYPE, COMBAT_ENERGYDAMAGE)
   setCombatParam(combat, COMBAT_PARAM_EFFECT, CONST_ME_FIREAREA)
   setCombatFormula(combat, COMBAT_FORMULA_SKILL, 0, -60, 0.8, 0)
   
   local area = createCombatArea(AREADIAGONAL_BEAM5)
setCombatArea(combat, area)


function onCastSpell(cid, var)
return doCombat(cid, combat, var)
end

o que esses 2 exatamente faz ?

"function onCastSpell(cid, var)"
"return doCombat(cid, combat, var)"

<instant name="Kamehameha" words="kamehameha" lvl="1" mana="40" prem="0" range="1000" needtarget="0" blockwalls="1" needweapon="1" exhaustion="1000000" groups="1,1500" icon="107" needlearn="0" event="script" value="attack/Kamehameha.lua">