Attribution theory defines the phenomenon by which individuals attempt to search for and define the causes of certain behaviors. The self-serving bias and actor-observer bias both fall under attribution theory.
The self-serving bias is when an individual attributes their successes to internal factors, and their failures to external factors.
The actor-observer bias is when individuals explain their own behavior through external circumstances when they are the "Actor" and explains the behavior of others through internal characteristics when another person is viewed as the "Actor". This occurs because individuals are very acclimated to how situational factors (External factors) might affect their own behavior, but are not as well able to relate situational factors to their influence on others' behavior.