Final answer:
Agoraphobia is a specific phobia characterized by intense fear and anxiety in situations where escape might be difficult. It is classified under anxiety disorders in psychology.
Step-by-step explanation:
Agoraphobia is a specific phobia classified under anxiety disorders in psychology. It is characterized by intense fear and anxiety in situations where escape might be difficult, such as crowded places, enclosed spaces, or being outside the home alone. Piper experiences agoraphobia because she has a strong fear of these situations, which leads to avoidance behavior.