The big three, side by side
| Property | Bitcoin | Ethereum | Tether (USDT) |
|---|---|---|---|
| What it is | Native cryptocurrency | Smart-contract platform + coin | USD-pegged stablecoin token |
| Ledger model | UTXO | Account model | ERC-20 / TRC-20 / SPL (per chain) |
| Consensus | Proof of Work | Proof of Stake | Inherits host chain |
| Fee asset | BTC | ETH | Host chain’s native token |
| Supply | Capped at 21M | No hard cap; partly burned | Minted/redeemed against reserves 1:1 |
| L2 approach | Lightning Network | Rollups (Arbitrum, OP, Base, ZK) | Natively issued on many chains |
| Primary use | Store of value / payments | Programmable money / DeFi | Payments, trading pair, settlement |
Go deeper — beyond the big three
Cross-chain mechanics (bridges, lock-and-mint, the wrong-network failure mode) are demonstrated step-by-step in the Cross-chain transfer lab. Layer 2 design (optimistic vs ZK, sequencers, data availability) is covered in the Technology unit.
Key takeaways
A one-page summary of Major Networks & Assets. Print it for quick reference.
- Bitcoin: UTXO + PoW, capped at 21M, halvings; Lightning is its L2; optimized for scarcity/security, not programmability.
- Ethereum: account model + PoS (post-Merge), ETH is the fee asset, smart contracts are the differentiator; rollups are its L2 family.
- Tether (USDT) is issued across many chains as separate deployments — redeemable 1:1 with the issuer but not directly fungible across chains.
- Natively issued vs bridged: bridged variants carry bridge risk on top of the underlying asset risk.
- THE KEY RULE: you pay gas in the chain’s native token, not the asset you’re moving — holding USDT on Arbitrum doesn’t let you send it; you need ETH too.
- Wrong-network sends (e.g. ERC-20 USDT to a Tron address) usually cause permanent loss — always confirm chain + asset match.
Unit check
80% to complete this unit5 questions
Pass the unit check (4 of 5) to complete this unit.