What is bitcoin

 a type of digital currency in which a record of transactions is maintained and new units of currency are generated by the computational solution of mathematical problems, and which operates independently of a central bank.

"Bitcoin has become a hot commodity among speculators"

a unit of bitcoin.

"bitcoins can be used for online transactions between individuals"

Bitcoin is a form of digital currency that aims to eliminate the need for central authorities such as banks or governments. Instead, Bitcoin uses blockchain technology to support peer-to-peer transactions between users on a decentralized networkHow Does Bitcoin Make Money? The Bitcoin network of miners makes money from Bitcoin by successfully validating blocks and being rewarded. Bitcoins are exchangeable for fiat currency via cryptocurrency exchanges and can be used to make purchases from merchants and retailers that accept them.