What is the difference between PTSD, GAD, social phobia, panic disorder, aggrophobia, social anxiety disorder?

for example if you had generalized anxiety disorder, how would you know that it wasn't PTSD?

what distinguishes them apart?

What's the difference? The person who does the diagnosis, or the particular things you emphasised on the day. These conditions are not real entities like physical diseases. If you have TB or whooping cough or chickenpox, there is clear evidence of this specific condition (eg antibodies) in your body. These psychological conditions aren't like that - the labels are just a way of trying to describe a set of symptoms and group very different patients together, to make it easier to think about (easier for the psychiatrists etc).

Each and every one of these conditions is diagnosed according to a checklist of symptoms - to give the label, a certain number of items on the list should be present, but it's all pretty woolly and the items on the various lists overlap a good deal. Plenty of people are diagnosed with one of these and at a later time with another - instead or as well as. This is a bit like saying "you're damp.... oh no, you're wet..... no, you're soaking..... oh look, that bit of you is drier than the rest". One person's 'wet' is another person's 'soaking' - well, you get the idea, I'm sure, even if the example isn't perfect.

The only thing that MIGHT make a clearer distinction is that PTSD derives from trauma - but not all trauma affects all people in the same way, and, particularly if the trauma was suffered in childhood (which can be long ongoing sorts of trauma like emotional abuse) the resultant psychological suffering can take many different forms.

The truth is that psychological suffering is completely unique to the individual. There can be some patterns in common with other people, but ultimately, it's essential for each patient to be seen as a unique person. Hence good individualised psychotherapy is the most effective treatment for anyone whose suffering fits any of these categories.

Post-traumatic stress disorder (PSTD) is brought about by extreme experiences. For example: being a survivor in World War II. Seeing death and destruction firsthand can have such a strong effect on the mind that the image, sound, odor can haunt the survivor long after the actual event has happened.

Generalized anxiety disorder (GAD) is generalized worrying about anything and everything that leads to loss of sleep (due to worry), fatiguablity (due to lack of rest), restlessness (due to worry), loss of concentration (due to something else occupying the mind), irritability (due to worry) and muscle tension (due to worry).

Social phobia (also known as Social Anxiety Disorder): the person is afraid of being humiliated/ embarassed by her/ his actions. An example will be public speaking.

Panic disorder: the body is very edgy and has fast heartbeat; lots of perspiration; short, insufficient breaths; dizziness, shaking. This episode happens even without threat to life.

Agoraphobia: fear of public spaces. Agoraphobia can cause panic disorder.