dApp
In short A dApp is an app whose core logic runs as smart contracts on a blockchain, so users interact through a wallet instead of an account on a company's server.
A dApp, short for decentralized application, is a program whose key logic lives in smart contracts deployed on a blockchain. The website you see is usually just a front end that reads on-chain data and helps you build transactions. Decentralized exchanges, lending markets, NFT marketplaces, and token launchpads all work this way.
Instead of creating an account with an email and password, you connect a crypto wallet. Connecting and reading data are free, because nothing is written to the chain. A network fee only applies when you send a state-changing transaction, such as a swap, a deposit, or a token approval, and the result is recorded publicly. The dApp asks your wallet to sign, and nothing happens on-chain until you approve.
Decentralized is a spectrum, not a yes or no. The contracts may be immutable, or they may sit behind an upgradeable proxy that the team can change at any time. The front end may be hosted on a normal web server that can be taken down or altered, or on decentralized storage such as IPFS or Arweave, which is harder to censor but still just serves files. Admin keys, oracles, and whoever can pause or modify the system decide how much you are trusting a team versus code.
This matters because you are the one holding the risk. There is no support desk to reverse a mistaken transaction or recover funds sent to a malicious contract. A fake site that looks identical to the real one can ask you to sign something that drains your wallet. Many of the worst losses for small-cap traders come from signing the wrong thing on a lookalike site, not from a broken protocol.
Before connecting, verify you are on the correct address, preferably one you bookmarked or reached from the project's official channels. Read what the wallet asks you to sign, especially unlimited token approvals and requests you do not recognize. Check whether the contract is verified on a block explorer, whether an audit exists, and who controls the admin functions. Using a separate wallet with only a small balance for new dApps limits the damage if something goes wrong.