the main innovation of cryptocurrency is that you can keep this digital record on all the computers on a peer to peer network without having to rely on a central authority to prevent any of the peers from double spending their balance.
an anonymous personality calling himself Satoshi Nakamoto first launched bitcoin in 2008. Since then over two thousand other cryptocurrency experiments have been launched. EXPAND for list of currencies.
The way to think of pricing cryptocurrency is as speculation above some floor determined by the growth of the network according to Metcalfe's law. There are also various other metrics that probably correspond to price like the number of transactions, the number of wallets, and the hash power wielded by the network.