Bitcoin is a purely digital means of payment whose accounts are secured by keys. You can use these to carry out transfers and thus have access to the inventory.
How can investors store and use bitcoins?
You keep bitcoins accounts called “addresses”. The bitcoin stock of an address results from the difference between all inflows and outflows.
In contrast to conventional bank accounts, however, there is no fundamental separation of “account number” and “PIN number”. Both keys already contain the information of the “account number”. However, the private key also contains the “PIN” at the same time. This allows full access to the entire inventory of the address to whoever is in possession of the private key.