Up to 2000 satoshi every 600 minutes. (ePay.info)
The value of a bitcoin is not tied or pegged to the value of any other currency. Similar to stocks or property, bitcoin's value is determined by buying and selling in the open market. A bitcoin's price changes in real time based on the number of people who want to buy or sell it at a given moment.
Bitcoin is traded for dollars, euros, yen, and other currencies in real time 24 hours a day. Depending on the demand for buying or selling bitcoin, the price can fluctuate from day to day. This is similar to the manner in which the value of a stock or property can go up or down based on supply and demand. Bitcoin's value can be volatile compared to traditional currencies such as the US dollar because it is still an emerging technology.
Unlike credit card networks like Visa and payment processors like Paypal, bitcoin is not owned by an individual or company. Bitcoin is the world's first completely open payment network which anyone with an internet connection can participate in. Bitcoin was designed to be used on the internet, and doesn't depend on banks or private companies to process transactions.
Bitcoin allows you to instantly send any amount of money to anyone in the world without needing a bank. It allows you to access your money without needing an ATM or credit card - bitcoin gives you back control over your money. Plus you can pay friends back for dinner, buy your next computer, and donate to charity, all using bitcoin.