Fear is a normal response for any animal to a fear-inducing stimulus or situation. As unpleasant as it may be to feel fear, it keeps our animals safe by encouraging caution and by preparing for fight or flight when danger threatens. Problems arise, however, if fears become so excessive and irrational that they disrupt normal functioning. At this stage, fear has crossed a divide and is now better classed as phobia.
For more information, please read Introduction to Feline Fears