Bitcoin is digital decentralized currency and a worldwide payment system.
Decentralized meaning it doesn’t require a central bank but is based on a technology called the blockchain.
Blockchain technology records publicly an immutable ledger of all transactions.
Transactions are based on cryptography and placed between users directly without an intermediary (bank).
Bitcoin price and value to exchange to fiat currencies or altcoins is based on supply and demand which is based on perceptions.