[I had a conversation with my client and he asked me something related to SEO. I am in this field for the past two years and have not heard these word AP sites. He asked me are you doing SEO by Ap sites? I was not in a condition to answer his question as don’t have knowledge of this. Please do share your knowledge about AP sites. I searched it on the net but did not get the appropriate answer.]
Context is everything in communications. Without knowing the context of your conversation, my first guess would be Associated Press, which is a news service. Aside from that, the only other place I have heard it used for is a biochemistry term. I can tell you that it is not a common SEO term, at least not in my experience and I have been involved for many years.
Why not just ask him to clarify what he meant by the term?