Bitcoin is a type of digital currency in P2P form, where transactions take place between users directly. These transactions are verified by network nodes and recorded in a public distributed ledger called a blockchain. The peer-to-peer transfer represents a decentralized payment system.
Unlike most currencies, the issue of bitcoin doesn’t rely on certain monetary authorities. Instead, it’s based on a specific algorithm and created through a large amount of calculation. The main difference between bitcoin and other virtual currencies is its limited overall quantity, resulting in great scarcity. There would only ever be 21 million bitcoins in total.
Besides being created as a reward for mining, bitcoin can be exchanged for other currencies, products, and services in legal or black markets.
Now the demand for mining machines is not only for bitcoins, but also a variety of other virtual currencies such as litecoin, ethereum, peercoin and a few others.