Item Scripts are quest scripts attached to Items. Items will load a script on the first event that triggers them and will load one and only one from the following location. Which ever it finds first in the following order:
The format of the item_script is as follows:
If ScriptFileID != 0
item_script = "script_" + ScriptFileID
Else If CharmFile != ""
item_script = CharmFile
item_script = item_id