Normally, a creature’s base power is the power printed on the card, or, for a token, the power set by the effect that created it. If another effect sets a creature’s power to a specific number or value, that becomes its base power. If an effect modifies a creature’s power without setting it, that is not included when determining its base power.

If a creature has a characteristic-defining ability that sets its power, indicated with a * or similar in the power and toughness box, that ability is taken into account when determining its base power.

Some creatures have base power 0 and an ability that gives them a bonus based on some criteria. Those are not characteristic-defining abilities, and that ability doesn’t change its base power. Such a creature will have power different from its base power if that ability causes its power to be anything other than 0.