There are numerous advertisements from pharmaceutical companies to consumers that list the symptoms of social anxiety disorder, and if you have these symptoms, you are encouraged to visit your doctor. However, there will be many more people with shyness rather than social anxiety disorder. Shyness is a normal personality trait, whereas social anxiety disorder, also known as social phobia, is a major anxiety disorder. Only social anxiety disorder requires treatment.
Shyness is being uncomfortable in social situations, whereas social anxiety disorder is the extreme fear of social scrutiny. Shyness does not necessarily make you avoid social situations. If you are shy, you may attend a party, you may even talk to other people, but you only have a discomfort, and are able to carry on a social interaction. Basically, you are able to chit chat when shy, but you may not always be able to initiate a conversation or initiate a fun outing with friends.
If you have social anxiety disorder, you have such an extreme fear of social scrutiny that you avoid social situations at all cost. In crowds of people, you think that they are making fun of you, judging you. However, avoiding social situations only serve to make the anxiety worse. But if you have to be confronted with social situations, you try to avoid as much social contact as you can: you might stand alone in an unoccupied corner of the room, you might avoid eye contact, you might avoid initiating any conversation, you might have more alcohol to take the edge off, you might make frequent visits to the bathroom, or you might decide to leave early.
Another form of social anxiety disorder is that you may have extreme fear of giving speeches, presentations, or performances. This is called performance anxiety. If you have the performance anxiety type of social anxiety disorder, you freeze on stage, or you avoid being in front of an audience. You can imagine this would have negative consequences for someone who makes their living as a performer or presenter.
So shyness is a normal trait, and does not require treatment. On the other hand, social anxiety disorder is highly disruptive to your life, and treatment is necessary. For more information on social anxiety disorder, read my book on anxiety, Anxiety Protocol. Anxiety Protocol can help you to eradicate anxiety from your life.