What's the diference between Social Anxiety Disorder and APD

I don't really understand the differences.

as far as i know, avpd is more severe than social anxiety.
also, a distinguishing feature of avpd is that we monitor not only ourselves but others as well.

this site explains it well
http://www.anxietyhelp.org/information/avpd_vs_sad.html

Yes, I would say that AvPD is like a very bad case of social anxiety. It is so bad that people avoid things that they should be doing, while people with social anxiety feel uncomfortable but somehow manage to do those things.