OpenSea is the largest marketplace for non-fungible tokens (NFTs), where people can buy and sell unique digital assets such as collectibles, art, and even virtual real estate. It operates on the Ethereum blockchain, allowing for secure transactions and ownership verification. OpenSea offers a vast selection of NFTs, ranging from one-of-a-kind pieces by top artists to rare in-game items. It also provides a platform for creators to easily list and sell their own NFTs.