## TL;DR

Cryptocurrency is digital money secured by cryptography, operating on decentralized networks (blockchains). Bitcoin (2009, Satoshi Nakamoto) was the first and remains the largest. Key concepts: decentralization, limited supply (Bitcoin capped at 21 million), mining/PoS consensus, wallets (public key = address, private key = access).

## Core Explanation

Bitcoin: deflationary (halving every 4 years, most recent 2024). Ethereum: smart contracts enable DeFi, NFTs. Stablecoins (USDT, USDC): pegged to fiat, reduce volatility. Altcoins: thousands of alternatives. Risks: extreme volatility, regulatory uncertainty, hacks/scams, environmental (PoW mining). Blockchain Trilemma: security, decentralization, scalability — improving two compromises the third. ETFs: Bitcoin ETF approved (SEC, Jan 2024) — mainstream adoption.

## Further Reading

- [The Bitcoin Standard (Saifedean Ammous)](https://www.wiley.com/en-us/The+Bitcoin+Standard%3A+The+Decentralized+Alternative+to+Central+Banking-p-9781119473862)