Web 3.0 dApps or decentralized applications are the digital applications or programs run on a decentralized, peer-to-peer Blockchain network. DApps are not under the control of a single entity, given that they run on a network of computers as opposed to a single computer or server.
Web 2.0 traditional apps such as Facebook and Twitter have backend codes running on centralized servers. They are owned and operated by an organization, granting full authority over the app and its workings.