Animal behavior is the actions an animal does in response to stimuli in their environment. The type of stimuli can be external or internal to the animal. The study of animal behavior is called ethology.
There are many different types of animal behavior. Most types behavior falls under or between the two main behaviors. Those two types are innate behavior and learned behavior. The animal starts with innate behavior, and works its way up to learned behavior, which is far more complex then the first type.
Types of behavior will go into more detail about the two main behaviors and the levels in between.