
xmls inside skills folder contain information about "skills"
all variables are handled by core. i will try to describe each one.
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 ---- L2J VARIABLES --
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Variable:

        PDAM,         - physycal damage skill
        MDAM          - magical damage
        DOT           - damage over time
        BLEED         - bleed
        POISON        - poison
        HEAL          - heal
        BALANCE_HEAL - balance hp skill 
        HOT - heal over time 
        COMBATPOINTHEAL - combat point heal
        CPHOT - cp heal over time
        MANAHEAL- mana heal 
        MANAHEAL_PERCENT mana heal percent
        MANARECHARGE - mana recharge
        MPHOT - hp heal over time
        AGGDAMAGE - agression damage
        BUFF - buff type
        DEBUFF - debuff type
        EXITBUFFS  - remove buff type
        NEEDCHARGE  - need charge type
        STUN - stun type
        ROOT - root type
        RESURRECT,
        PASSIVE,
        CONT,
        CONFUSION,
        UNLOCK,
        CHARGE               
        FEAR,
        MHOT,
        DRAIN             
        NEGATE,               
        CANCEL,             
        SLEEP,
        AGGREDUCE,
        AGGREMOVE,
        AGGREDUCE_CHAR,
        CHARGEDAM         
        CONFUSE_MOB_ONLY,
        DEATHLINK,
        BLOW,
        FATALCOUNTER,
        DETECT_WEAKNESS,
        ENCHANT_ARMOR,
        ENCHANT_WEAPON,
        FEED_PET,
        HEAL_PERCENT,
        HEAL_STATIC,
        LUCK,
        MANADAM,
        MDOT,
        MUTE,
        RECALL,
        REFLECT,
        SUMMON_FRIEND,        
        SOULSHOT,
        SPIRITSHOT,
        SPOIL,
        SWEEP,
        SUMMON             
        WEAKNESS,
        DEATHLINK_PET,
        MANA_BY_LEVEL,
        FAKE_DEATH,
        UNBLEED,
        UNPOISON,
        SIEGEFLAG,
        TAKECASTLE,
        UNDEAD_DEFENSE,
        SEED                
        BEAST_FEED,        
        PARALYZE,
        DRAIN_SOUL,
        COMMON_CRAFT, 
        DWARVEN_CRAFT,
        WEAPON_SA,
        DELUXE_KEY_UNLOCK,
        FISHING,
        PUMPING,
        REELING,
        CANCEL_TARGET,
        CHARGE_SELF,
        CRITS,
        CREATE_ITEM   
        AGGDEBUFF,
        COMBATPOINTPERHEAL,
        SUMMONCP,
        SUMMON_TREASURE_KEY,
        SUMMON_CURSED_BONES,
        ERASE,
        MAGE_BANE, 
        WARRIOR_BANE,
        STRSIEGEASSAULT, 
        LUCKNOBLESSE
        RAID_DESCRIPTION,
        UNSUMMON_ENEMY_PET,
        BETRAY,
        BALANCE_LIFE,
        NOTDONE - skill not implemented.

Variable:

		<set name="target" val="val"/>
 
 Options: 
        TARGET_NONE - no target, this skill is not implemented yet.
        TARGET_SELF - target is caster.
        TARGET_ONE - any other target.
        TARGET_PARTY  - target is caster party
        TARGET_ALLY - target is caster ally
        TARGET_CLAN - target is caster clan
        TARGET_PET - target is a pet
        TARGET_AREA - target is the area of caster (depending on radius set)
        TARGET_AURA - target is the area of caster (depending on radius set), uses caster as center.
        TARGET_CORPSE - target is a corpse of a mob.
        TARGET_AREA_UNDEAD - target is a undead type moster
        TARGET_MULTIFACE - used for gladiators 
        TARGET_CORPSE_ALLY - target is caster ally member corpse.
        TARGET_CORPSE_CLAN   - target is caster clan member corpse.
        TARGET_CORPSE_PLAYER - target is a corpse of a player
        TARGET_CORPSE_PET - target is the corpse of a pet.
        TARGET_ITEM -- ??
        TARGET_AREA_CORPSE_MOB - target is all mob corpses in a area(depending on radius set) 
        TARGET_CORPSE_MOB --??
        TARGET_UNLOCKABLE -- target is a chest/door
        TARGET_HOLY - target is holy artefact
        TARGET_PARTY_MEMBER  - target is a party member
        TARGET_ENEMY_SUMMON  - target is an anemy summon
        TARGET_OWNER_PET
        TARGET_ENEMY_ALLY
        TARGET_ENEMY_PET
        TARGET_GATE
        TARGET_MOB
        TARGET_AREA_MOB
        TARGET_KNOWNLIST
        TARGET_COUPLE
 
Variable:

<set name="operateType" val="value"/> - defines to core how this skill will be used passive or active.
 
 Options: OP_ACTIVE / OP_PASSIVE

Variable:

<set name="reuseDelay" val="(time in miliseconds)"/>  - sets the re use delay of skill.

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-- L2Emu Variables ----
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<set name="isSymbol" val="(boolean)"/> - determines that a skill is a symbol type.

     Exemple: Symbol of Defense.
     
<set name="isForce" val="(boolean)"/> - determines that a skill is a force type.

   Exemple: battle Force.