In contrast to normal variation in baseline anxiety levels, individuals with anxiety disorders such as panic disorder, agoraphobia and specific phobias (formerly called simple phobias) are often severely handicapped by their fear. People with panic disorder experience unprovoked panic attacks with terrifying fear and physical signs of panic, such as increased heart rate, sweating and feeling choked. Agoraphobia is characterized by fear of being in public places and often co-exists with panic disorder, whereas specific phobias are characterized by intense, unreasonable fear of specific things (such as spiders, snakes or lightening) or situations (flying an airplane or having blood drawn)
I hope this helps!