Key Concepts
| Term | Definition |
|---|
| Blockchain | Decentralized, immutable digital ledger — transactions grouped in blocks |
| Bitcoin (BTC) | First cryptocurrency — peer-to-peer digital cash, 21M supply cap |
| Ethereum (ETH) | Programmable blockchain — smart contracts, DeFi, NFTs |
| Wallet | Software/hardware that stores private keys — NOT the coins themselves |
| Private Key | Secret 256-bit number — whoever has it controls the funds. Never share it. |
| Seed Phrase | 12-24 words that restore your wallet — store offline, never digital |
Wallet Types
| Type | Security | Best For |
|---|
| Hardware (Ledger, Trezor) | Highest | Long-term storage, large amounts |
| Software (Metamask, Trust) | Medium | DeFi, daily use, smaller amounts |
| Exchange (Coinbase, Binance) | Lowest | Trading only — not your keys, not your coins |
| Paper | High (offline) | Cold storage — risk of physical loss |
Security Essentials
| Rule | Why |
|---|
| Never share your seed phrase | Anyone with it controls your funds — no recovery, no undo |
| Use hardware wallet for >$1K | Software wallets can be compromised by malware |
| Enable 2FA (NOT SMS) | Use authenticator app or hardware key — SIM swap attacks are real |
| Verify addresses | Always check first/last 4 chars of address before sending |
Common Scams
| Scam | Red Flag |
|---|
| Fake support DMs | No legit project DMs you first about wallet issues |
| Giveaway scams | "Send 1 ETH, get 2 ETH back" — no one doubles your money for free |
| Phishing sites | Check URLs carefully — bookmark real sites, never Google search them |
Pro Tip: Not your keys, not your coins. Exchanges are for trading, not storing. Move crypto to a hardware wallet for anything you plan to hold longer than a week. FTX, Mt. Gox, and Quadriga taught us this the hard way.