OpenSea is a marketplace for the decentralized web, including crypto collectibles, gaming items, and other items that are backed by the Ethereum blockchain. On OpenSea, you can buy or sell any of these items through an Ethereum smart contract, meaning that no central authority ever holds custody of your items.
Band Protocol provides a standard framework for the decentralized management of data, serving as a fundamental query layer for applications that requires access to off-chain information. This eliminates the critical centralizing trust and points of failure that the oracle problem typically introduces to decentralized applications with other designs.
Reality.eth provides a flexible mechanism for verifying real-world events for smart contracts. Using a system of escalating bonds, it allows anyone to post a question, and anyone to answer. Questions can be posted either through the reality.eth dapp or through your own UI talking directly to the contract, and any contract can read the answers on-chain.