ERC-1155

ERC-1155 is the Ethereum multi-token standard — one contract holds many token types, each can be fungible or non-fungible. Instead of balance-per-address (ERC-20) or owner-per-ID (ERC-721), it's balance-per-(address, id): token ID 1 might have supply 1000 (fungible potions), ID 2 might have supply 1 (a unique sword), all in the same contract. Two wins that drove adoption: batch operations — safeBatchTransferFrom moves many token types in one transaction, dramatically cheaper than N separate ERC-20/721 calls; deployment efficiency — one contract instead of one per token type. Originally designed by Enjin for gaming, now used widely for in-game assets, event tickets, fractional NFTs, and semi-fungible collections (e.g. editions of 100). The trade: less tooling support than pure ERC-20 / ERC-721 since it's a superset; simple use cases still prefer the older standards for ecosystem maturity.