This is a fear associated with a specific object or situation. The person is terrified, even though the danger isn’t real (or it’s not as critical as the person thinks). Common specific phobias include phobias of animals, insects, storms, heights, closed spaces, etc.
In a situation, or when they think of that situation, the person with a phobia feels anxiety, including a variety of physical sensations: their heart may race, they may feel dizzy or get the shakes, they may start sweating, have a stomach-ache, get confused, etc.
Phobia is physical! Not everyone has a phobia, and just because you think spiders are gross, it doesn’t mean you have arachnophobia!