OpenSea

OpenSea is a marketplace for non-fungible tokens. A seller lists an item by signing an order, and the transfer settles on-chain when a buyer accepts, which means the marketplace itself never holds the asset. The product is organised around collections. A collection groups tokens that share a contract and a theme, and its page shows floor price, volume, and listed items. That structure is what makes a large set of individually distinct tokens navigable, and it is why the marketplace became the default place to look up a collection's activity. The tradeoffs are the marketplace's and the asset's. Listing is free because it is only a signature, but settlement costs gas, and a listing can be bypassed if the same asset is sold elsewhere. Fees and royalty enforcement have changed repeatedly, which matters to creators whose income depended on secondary sales.