Well obviously no one knows... or very few people know (I still think that there are a couple original bitcoiners on this forum who are 99% sure that they know who Satoshi is).
Whats your favourite theory?
Mine is that it was John Nash

Please provide some proof for your theories. Would love to look into them!
Satoshi Nakamoto is the name used by the unknown person or persons who developed bitcoin. He authored the bitcoin white paper, and created bitcoin's original reference implementation. They were the first to solve the problem for digital currency using a peer-to-peer network.