Innate level
The innate level of a spell is what is considered its spell level for the purposes of feats such as craft wand and brew potion. This is especially important where different casting classes receive the same spell at different spell levels.
It also is the level that monster special abilities use, such as spells known by a Balor or a Dragon, who do not have any classes in a normal spellcasting class.
Gameplay Notes
Innate level on NWN2/BGTSCC does not function as described. Unlike as written, spells use the caster's own spellbook as reference for what level spells are available. For instance, although True Seeing's Innate Level of 5 implies it is impossible to be made as a wand, it is fact that Knowledge (domain) clerics can create wands of True Seeing, falsifying the information on this page.