This is the biggest attendance at a sporting event held in an enclosed stadium. The crowd number is an unofficial number - the official crowd (people who paid tickets) that day was 173,850. Due to its large capacity, Maracana stadium has many more reported sporting events with large attendance figures.
Bitcoin is a digital currency (also called crypto-currency) that is not backed by any country's central bank or government. Bitcoins can be traded for goods or services with vendors who accept Bitcoins as payment.
Bitcoin is a new and interesting electronic currency, the value of which is not backed by any single government or organization. Like other currencies, it is worth something partly because people are willing to trade it for goods and services. Its exchange rate fluctuates continuously, and sometimes wildly.