1) Like Xeroc said you can store anything basically on a blockchain. You can also have many different currencies on the Bitcoin blockchain. Google "colored coins".
DAC = is a general metaphor that not only applies to Bitshares projects. Google "Decentralized autonomous company".
Bitshares = is the name for the whole Bitshares project. If I would have to define the Bitshares project with only a few words I would say: One chain for one application, DPOS to secure/maintain the chain, Making use of blockchain technology for various (decentralized/decentralizeable) business models.
AGS/PTS holders will in most cases hold a big share in many Bitshares DACs and receive profits/dividends in case that is what these shareholders want. The shareholders could also decide (by electing delegates) that the profits should be reinvested in the growth of the DAC (marketing etc.).
Hope it helps! Keep on asking your questions, they make sense