Decentralized Apps (dApps) are blockchain-backed digital applications that run on a peer-to-peer network. The primary distinguishing factor of dApps is that they are not operated by a single entity, unlike conventional applications. Instead, they are automatically operated through the use of smart contracts. Most dApps are centered and built on the Ethereum blockchain, although some dApps run on other public blockchain platforms.
The primary benefit of dApps (over conventional applications) is the low risk of manipulation. dApp systems are more trustworthy given that they are not modifiable, and they are equally free from centralized control. The most popular dApp for trading NFTs is OpenSea.
You can see more dApps and track their progress on stateofthedapps.com.