Bitcoin is a digital token that can be sent electronically from one user to another, anywhere in the world. Bitcoin mining software is also very well known software for use bitcoin.
Bitcoin is also the name of the payment network on which the Bitcoin digital tokens move. Some people differentiate between Bitcoin capitalized, as the token, and bitcoin lowercase, as the network. Unlike traditional payment networks like Visa or American Express, no single company or person runs the Bitcoin network. Instead, it is a decentralized network of computers around the world that keep track of all Bitcoin transactions, similar to the decentralized network of servers that makes the internet work.
Because there is no central authority running Bitcoin, no one has the authority to force new users to reveal their identities. The network was designed this way to create a currency and a financial network outside the control of any government or single company.