Anyone who has ever had one knows that a panic attack is an extremely unpleasant and frightening experience. It is often mistaken for the symptoms of a heart attack - which means it's quite common for people to call an ambulance when suffering from a panic attack. Although it feels like something terrible is happening to the body, panic attacks in themselves are not dangerous to us.
So what is panic? What we mean by panic is the extreme level of anxiety. One easy way to understand this is by rating our level of anxiety - say out of 10. Going for a job interview might cause an anxiety level of around 5/10 - going to the dentist might raise this to 7/10 (depending probably on our previous experience of dentists). A panic attack is a 10/10 - it's the most anxiety we can feel. For that reason, it's an intense, usually fairly short-lived, experience.
Why does it feel like it goes on for a long time? Some people report feeling like they are panicking for hours on end. It is probably more helpful to think of this as a series of panic attacks - with the level of anxiety going up and down between around 8 and 10. There's a good reason for this - our bodies simply won't sustain a 10/10 level - the body decides at some point that it is not in danger and starts to calm down (although it doesn't feel calm!) It rises again to panic level when our fear is re-triggered. This process of going in and out of panic can go on for a long time.
What causes a panic attack? At a physiological (bodily) level our body/mind system is going into the fight/flight mechanism - it has sensed danger and is getting ready to fight it or escape it. The problem with panic is that the fight/flight mechanism gets activated when there is no 'real' danger, only a perceived one. For example, getting into a lift is not, in itself, a particularly dangerous activity. For some people, however, getting into a lift 'feels like' a frightening experience and they have a panic attack. The problem is over-estimating the risk involved in getting into a lift, ie 'I won't be able to breathe', 'the lift will stop and I'll panic' ,'I'll go crazy', 'I'll lose control', etc. Having a problem with panic means you become a 'bad gambler', unable to accurately assess the risk in certain situations. For instance, many people who are afraid of flying or going to busy places will happily drive a car, which on a purely rational level is a more risky situation. It's very understandable that logic goes out of the window when we panic because our body/mind is not in a fit state to make rational decisions - it's just trying to survive.
So a panic attack is the body/mind going into the fight/flight mechanism, - triggered by something we see as dangerous and frightening. Sometimes it's very hard to work out what this dangerous and frightening thing is - the 'feared consequence'. It can often feel like the panic comes out of the blue, without any obvious trigger. In order to help with panic attacks it's important to work out what is triggering them and what is the underlying fear.
Psychotherapy for Panic Attacks: Psychotherapy can be useful in working out what is causing the panic. Once you have worked out with a therapist what is going on, then you can decide how to work on it. Panic attacks are a symptom and may be related to lots of different kinds of problems - not necessarily 'Panic Disorder'.
If you'd like to read more about 'Panic Disorder' then go to: http://www.nhs.uk/conditions/Panic-disorder/Pages/Introduction.aspx