Centralized Applications or Traditional Application uses two important elements called front end and Back end. Here a single server will contain all the logic to conduct the further necessary steps. The Server will receive your request, process it, saves what it needs, and returns the correct response.
With Decentralized Applications, all nodes in a network receive the logic that is stored within your contract. Once the contract is mined, then all the nodes in the network will receive the same logic and it will be saved on the Blockchain. When you interact with the contract, the same signal must be processed with the stored logic.
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