How do a panic attack and a anxiety attack differ?

Panic attacks are: Sudden, intense, usually brief anxiety attacks & may be mistaken for a heart attack or other life-threatening condition. If they reoccur unpredictably, they can be called panic disorder. Avoiding certain types of places associated with an attack is called agoraphobia. Anxiety can be milder, more predictable or more general, including chronic worry. Panic & anxiety attacks are often synonymous.