Whats the technical/database entity of a crypto-currency / Bitcoin?
A bitcoin, as defined in the whitepaper, is a chain of digital signatures. "To own 1 bitcoin" is by definition equivalent to the following: "in the history of transactions, as defined by the heaviest blockchain branch originating from the genesis block, there exist unspent transaction outputs that sum up to 1 bitcoin such that you have the private key(s) required to spend them".