The difference between dApps and smart contracts
Decentralized applications include the full package of front-end (what the user sees) and back-end (the app algorithms behind it). Smart contracts, on the other hand, consist only of the back-end algorithms. This means that if you want to create a decentralized application on a smart contract system (i.e. not with Lisk), you have to combine several smart contracts and rely on third party systems for the front-end.