dolby pro logic and The Roots

Can any one explain in relative layman's terms how Dolby pro logic II works? Assume sound recording knowledge, but very little when it comes to acoustics/physics. Thanks in advance. Zach PS I saw the Roots on TV last night; they were amazing. I'm going to buy one of their CDs as soon as I'm able. Any suggestions for a starting point? They were playing from Phrenology in this particular concert.