A Dapp is a ‘blockchain enabled’ website, where the Smart Contract is what allows it to connect to the blockchain.
The easiest way to understand this is to understand how traditional websites operate.
You can think of a website like this:
Front End → API → Database
A Dapp is very similar to a traditional web application. The front end uses the exact same technology to render the page. The one critical difference is that instead of an API connecting to a Database, you have a Smart Contract connecting to a blockchain.
You can think of a Dapp like this:
Front End → Smart Contract → Blockchain
While a simplified version of what’s happening, this does illustrate that Smart Contracts are playing the role of the ‘api connector’ to the blockchain.
Originally posted through Quora.