They may occur often or just occasionally. They can cripple the person. It can keep people isolated in the home for fear of going out. Anxiety issues are somewhat different. People who feel anxious have a constant dread or uncomfortable feeling that affects them on a daily basis.
Anxieties can present in different ways.
A phobia is a type of anxiety with an intensity resembling panic. Some cannot use a public restroom. Many try to cover this up by coming up with excuses and it can create serious relationship issues. There is performance anxiety, where even a skilled professional freezes in front of people. It is sometimes called stage fright.