What is the difference between generalized anxiety disorder and panic disorder?

Generalized anxiety disorder, or GAD, involves persistent, excessive worry about multiple everyday topics like health, finances, and work for at least six months. Physical symptoms include muscle tension, fatigue, restlessness, and sleep disturbance. The worry is disproportionate to actual circumstances. Panic disorder involves recurrent unexpected panic attacks, which are sudden episodes of intense fear peaking within minutes, with physical symptoms like racing heart, shortness of breath, dizziness, and feeling of impending doom.