What I found out:
"A decentralized application is a computer application that runs on a distributed computing system. DApps have been popularized by distributed ledger technologies (DLT) such as the Ethereum Blockchain, where DApps are often referred to as smart contracts.
As the concept is still in its infancy, there might not be one definition of what a Dapp is. However, there are noticeable common features of Dapps:
Open Source. Ideally, it should be governed by autonomy and all changes must be decided by the consensus, or a majority, of its users. Its code base should be available for scrutiny.
+Decentralized. All records of the application’s operation must be stored on a public and decentralized blockchain to avoid pitfalls of centralization.
+Incentivized. Validators of the blockchain should be incentivized by rewarding them accordingly with cryptographic tokens.
+Protocol. The application community must agree on a cryptographic algorithm to show proof of value. For example, Bitcoin uses Proof of Work (PoW) and Ethereum is currently using PoW with plans for a hybrid PoW/Proof of Stake (PoS)5 in the future.
If we adhere to the above definition, the first Dapp was in fact bitcoin itself. bitcoin is an implemented blockchain solution that arose from problems revolving around centralization and censorship. One can say Bitcoin is a self-sustaining public ledger that allows efficient transactions without intermediaries and centralized authorities."
As far as I understand, crypto projects are built on blockchain platforms, i.e. each project will build a decentralized platform, or that platform itself is a Dapp for users. If the project can't do that, they can't deliver on what they promised in WhitePaper, that is they failed or was a scam project.