Bitcoin is digital currency released in 2008. It is the world’s first and biggest cryptocurrency, since its operation, functioning and issuance are based on the principles of cryptography.
Bitcoin was released in 2008, on the heels of the housing bubble and crash, by an individual or group of people working under the pseudonym Satoshi Nakamoto. The Bitcoin whitepaper released by Satoshi Nakamoto elaborated on the principles and motivations behind Bitcoin’s introduction and its real-world utility.
Since the housing bubble crisis was majorly attributed to the abuse of financial power by big banks and financial entities, Bitcoin’s launch was based on the ideals of eradicating this centralized power and giving people power over their money.
This is why Bitcoin is a decentralized currency. No single authority can govern Bitcoin. Instead, it operates as a peer-to-peer network. Each network entity is called a 'node' and exerts equal power in the network. All this is enabled by blockchain technology, which forms the bedrock of Bitcoin’s functioning.
The blockchain is immutable, and transparent. So all nodes in a network can see every transaction, and every wallet/s balance. Simultaneously, they are also practically prohibited from changing these, since any change requires the consensus of a majority (51%+) of the network. Every node in the Bitcoin network saves its copy of the blockchain.