An approach is a perspective (i.e. view) that involves certain assumptions (i.e. beliefs) about human behavior: the way they function, which aspects of them are worthy of study, and what research methods are appropriate for undertaking this study.
There may be several different theories within an approach, but they all share these common assumptions. You may wonder why there are so many different psychology perspectives and whether one approach is correct and others wrong.
Most psychologists would agree that no one perspective is correct, although in the past, in the early days of psychology, the behaviorist would have said their perspective was the only truly scientific one.
Each perspective has its strengths and weaknesses and brings something different to our understanding of human behavior. For this reason, it is important that psychology does have different perspectives to the understanding and study of human and animal behavior.