Bitcoin is a payment system introduced as open-source software in 2009 by developer Satoshi Nakamoto. The payments in the system are recorded in a public ledger using its own unit of account, which is also called bitcoin. Payments work peer-to-peer without a central repository or single administrator, which has led the US Treasury to call bitcoin a decentralized virtual currency. Although its status as a currency is disputed, media reports often refer to bitcoin as a cryptocurrency or digital currency.
To win free extra bitcoins here, all you need is a bitcoin wallet. You can easily create one from http://blockchain.info for example. Then, you enter it after you login, solve the two captchas and win the bitcoins.