How did Bitcoin start out?
Bitcoin is an experimental new digital currency that enables instant payments to anyone, anywhere in the world. Bitcoin uses peer-to-peer technology to operate with no central authority: managing transactions and issuing money are carried out collectively by the network. Bitcoin is also the name of the open source software which enables the use of this currency.
Bitcoin Client Software
Bitcoin is a system of merchants, individuals, a network of participants and software. Together they maintain a mutually co-operating infrastructure without the need for authorities - a decentralised peer-to-peer system. A core layer of the Bitcoin system is the Bitcoin network through which people interact with it using Bitcoin client software. Below we list such software.
Bitcoin clients are the base level of technology for conducting Bitcoin transactions. Clients usually store a collection of keys on that computer (often termed a wallet). These keys allow you to send and receive payments through the Bitcoin network. Nobody has access to these keys except yourself, and they must be kept secure. This is where clients differ, with ingenious strategies and ongoing research into making a user-friendly and secure client - not an easy task when both goals often conflict!
The original software written by Satoshi Nakamoto, the project's founder. If you aren't sure which program to pick, this is a good bet. This application is a peer-to-peer client that builds the backbone of the Bitcoin network. It is suited for enthusiasts, merchants, miners, developers and people who want to help support the project. People who run Bitcoin-Qt are first class network citizens and have the highest levels of security, privacy and stability. However, it can be very resource intensive and you should be willing to leave it running in the background so other computers can connect to yours. If your computer is low powered or you aren't willing to tolerate a 8-hour+ initial start time, you should consider other clients. Cutting edge features tend to be implemented in other clients first.
MultiBit's primary focus is being fast and easy to use, even for people with no technical knowledge. It has a YouTube channel to help you learn the software, and includes helpful features such as an exchange rate ticker. MultiBit supports many languages such as German, Spanish and Greek. MultiBit synchronizes with the network much faster than Bitcoin-Qt and should be ready for you to use within a few minutes. This is a good choice for non technical users who want an easy to use experience, especially if you use a Mac.
Armory is a Bitcoin client that works on top of Bitcoin-Qt, expanding it with functionality for Bitcoin power users. It focuses on advanced features and security options, including "cold-storage" for maintaining Bitcoins on an offline computer to protect your funds from online threats. Armory supports multiple encrypted wallets, each of which only needs to be backed up once using a printer or removable media. Armory is a good choice for experienced Bitcoin users, seeking additional flexibility and security for managing their funds.