Firstly a disclaimer. I have never done pair Programming. Never read officially about it I.e. Kent Becks Extreme Programming Explained. I have only what I have read in blogs, which is limited and my own thoughts. 
I feel it is important to document my ignorant understanding before I embark on learning as it gives a base level of my understanding based on what I currently know about agile methods which I can look at in the near or distant future and see my progress. 

Now, for my ideas on pair Programming .

Say you have 2 people, A and B. A has knowledge that B needs.

First phase, A and B sit together. A works while B observes. B can ask questions, but A explains as they go along what they are dong.

Second phase, B takes over while A observes. B applies the knowledge they have learned, while A corrects B for any mistakes or answers any questions as required.

At the end of both phases, you now have 2 people converse in the knowledge.

Now it it time for the third phase. B now teaches C and simultaneously, A can teach D if required.

This I see as a good way to disseminate knowledge through a group. You get the one on one time and then apply the knowledge through teaching. 

I first saw something similar in a TV show. ER as a method for surgeons to disseminate knowledge. The saying was…

• See one
• Do one
• Teach one

Now, as I mentioned earlier, this is my ignorant thoughts, but I would like to know everyone else’s on the topic. Let me know in the comments.