Animal Infusion allows the caster to take on one extraordinary ability or duplicate the ranks in one skill from any animal for the duration of the spell. The type of animal and the chosen ability or skill can change each time the spell is cast. Specific animal abilities can be found in Chapter 2 of the Monster Manual (pages 268-283).
For example, a caster who chose to infuse the spirit of a cheetah could choose from the cheetah's trip or sprint (allowing him to move 10 times his normal speed) extraordinary abilities, or to take any one of the cheetah's skills at the cheetah's ranks in that skill, such as Move Silently +8 (which replaces any ranks the caster has in Move Silently for the duration of the spell).
Material component: A piece of the animal whose power you are going to gain. This can be fur, a feather, a claw, or any other item from the animal.