Fear is a natural reaction to a potentially dangerous situation. eg standing on the edge of a cliff, flying through turbulence, coming face to face with a lion. Your heart may beat faster, your breathing may become rapid and shallow and you might feel a little clammy.
A phobia is a fear taken to an extreme point with correspondingly increased physical symptoms. Very rapid shallow breathing, heart thumping wildly, feeling really cold and clammy, faint and woozy, anxious, panicky : in a heightened, alert state. Someone with a phobia will be constantly on the look out for the phobic object and will go to extreme lengths to avoid it. They may be able to pinpoint the incident which caused the phobia or the exact moment when they first experienced it.
Hypnotherapy can help by creating a state of relaxation; a chance to explore the phobia and the reasons behind it: and a way to diminish and extinguish it.