Otherwise known as Animal Lore, Creature Lore is used primarily for two effects.
For one it allows you to obtain a handful of information about creatures.
It also allows you to benefit from dodge and damage bonuses from your mounts.
Using Creature Lore on a creature also tells you about their race and hunger condition, and with over 30% skill, using the skill also yields the Taming skill required to try and tame the creature.
For creatures which have any means of resisting Provocation, it yields the Provocation skill required as well.
For mounts it shows information on the Damage and Dodge bonuses as well as the minimum Creature Lore required in order to ride them.