The AI_LEVEL_* constants are used in NWScript to indicate the priority given to a creature's demands on processing power (CPU time). This primarily affects AI, with higher priorities allowing more intelligent behavior. While it is usually bad practice to rely on the precise value of a symbolic constant, it can be assumed that the values from "very low" to "very high" are in increasing numeric order. For example, the conditional GetAILevel(oCreature) <= AI_LEVEL_LOW tests oCreature for having a "low" or "very low" AI level.