Bitcoin is a decentralized electronic currency conceived in 2009 by Satoshi Nakamoto. The name also applies to the protocol designed by the same author as the P2P network that supports it. Unlike most currencies, Bitcoin confidence does not depend on any central transmitter but uses a working test system to prevent double spending and reach consensus among all nodes.
Although there are coins and banknotes produced by individuals and companies, usually bitcoins to trade with clients are used, which can be native apps or web apps.
Native applications are installed and run directly on computers or mobile devices. Native Customers can also run automatically when the user clicks on a link on a web browser that complies with the format of the URI scheme specification bitcoin as registered with IANA.
Web applications need only a browser, and thus are accessible from all platforms, whether desktop (Windows, Linux, Mac OS X) or mobile (Android, iPhone, BlackBerry ...). Some web applications provide additional security access to bitcoins using two-factor authentication with SMS messages, email, specific devices and Google Authenticator.
The Bitcoins contain the public address of the current owner. When user A transfers something to a user B, A property delivery adding B's public key and then signed with its private key. A then includes those bitcoins in a transaction, and spread to the nodes of the P2P network to which it is connected. These nodes validate the cryptographic signatures and the value of the transaction before you accept and relay. This procedure propagates the transaction indefinitely to reach all nodes in the P2P network.