TL;DR
Bitcoin (2009, Satoshi Nakamoto) is the first decentralized digital currency, built on a blockchain ledger and proof of work, enabling transfers without a trusted third party. Supply is capped at 21 million BTC with issuance halving every ~4 years.
Key Points
- Blockchain: an append-only public ledger; each block links to the previous hash, so tampering requires redoing all subsequent work.
- Proof of work: miners race to find a hash below a difficulty target; energy use is the cost of security.
- Supply & halving: block reward halves every 210,000 blocks (~4 years); issuance approaches zero around 2140.
- Keys: private keys sign transactions; public keys/addresses receive; losing a private key means permanent loss.
- UTXO model: transactions consume old outputs and create new ones.
- Caveat: extreme price volatility; not investment advice.
Sources
- Nakamoto, "Bitcoin: A Peer-to-Peer Electronic Cash System" (2008)
- Wikipedia: Bitcoin / Blockchain
- Bitcoin Core documentation