“Smart contract” describes a delivery mechanism, not one monolithic design. In practice, builders combine a handful of archetypes—asset ledgers, access control modules, governance registries, and financial primitives—to ship marketplaces, treasuries, games, and enterprise workflows. Recognizing the category helps you reuse audited patterns and communicate clearly with legal and security reviewers.
Fungible token contracts
Fungible token standards (for example ERC-20 on Ethereum-compatible chains) implement a shared ledger of balances: mint, burn, transfer, and allowances. They power stablecoins, reward points, governance votes weighted by stake, and cross-protocol collateral. The contract’s risk surface is concentrated in mint authority, upgradeability, and any hooks that call external contracts during transfers.
Non-fungible and semi-fungible contracts
NFT standards (such as ERC-721 and ERC-1155) bind unique or batched token IDs to metadata URIs, royalty configurations, or in-game attributes. Semi-fungible IDs can represent a class of items with a finite supply—tickets, tiered passes, or loot tables—while still benefiting from the same wallet and marketplace infrastructure.
Governance and DAO contracts
Decentralized autonomous organizations typically separate token accounting, proposal creation, voting tallies, and timelocked execution. Multisignature modules often sit beside on-chain voting to handle emergencies. The type system here is procedural: who may propose, how quorum is calculated, and how long the community has to react before code changes go live.
Escrow, vesting, and payment streaming
Time-locked releases, milestone escrow, and streaming payments encode business rhythm on-chain. These contracts intersect heavily with compliance: who can claw back, what happens when a party disputes delivery, and how oracles supply external facts. Simplicity and formal verification matter because bugs directly move money.
DeFi primitives
- Automated market makers and liquidity pools for price discovery.
- Lending protocols with collateralization ratios and liquidation auctions.
- Derivatives and structured products that compose multiple contracts.
Choosing a type starts from the coordination problem: who needs to agree, what must be immutable, and what data must be public. Combine types deliberately—governance token plus treasury vault plus NFT access gate—and document invariants so auditors and users share the same mental model.