A user can have one or more bitcoin addresses from which bitcoins are sent or received using either a website or downloaded software often called a "wallet" like a digital wallet. Users can obtain new bitcoin addresses as needed. Many bitcoin services provide addresses tied to a user's individual account to hold funds on the user's behalf.
Specifically, a bitcoin address is a cryptographic public key[1] –– human-readable strings of numbers and letters around 33 characters in length, beginning with the digit 1 or 3, as in the example of 175tWpb8K1S7NmH4Zx6rewF9WQrcZv245W.[18] The matching private key is often stored in a digital wallet or mobile device and protected by a password or other means of authentication. Each bitcoin transaction is signed by the private key of the user initiating the transaction.
Various vendors offer banknotes and coins denominated in bitcoins; what is sold is really a bitcoin private key as part of the coin or banknote. Usually, a seal has to be broken to access the key, while the receiving address remains visible on the outside so that the balance can be