According to Dan Larimer one of the creators: BitShares is many things,
BitShares is a small town on global scale.
According to http://docs.bitshares.org/bitshares/whatis.html
BitShares is a technology supported by next generation entrepreneurs, investors, and developers with a common interest in finding free market solutions by leveraging the power of globally decentralized consensus and decision making.
BitShares does for business what bitcoin did for money by utilizing distributed consensus technology to create companies that are inherently global, transparent, trustworthy, efficient and most importantly profitable.
Consensus technology has the power to do for economics what the internet did for information.
BitShares looks to extend the innovation of the blockchain to all industries that rely upon the internet to provide their services.
More info on bitshares banking: https://bytemaster.github.io/article/2014/12/20/BitShares-as-a-Bank/