Dapp code hosted and executed on-chain
Smart contracts on the Internet Computer serve web content directly to users. This is a distinguishing feature, on other blockchains a small part of the dapp logic runs in a smart contract, but the actual consumer-facing web or interface is hosted on a centralized cloud provider (e.g. AWS) instead of being served directly from the blockchain.
The Internet Computer serving dapps whose code is hosted and executed entirely on-chain unlocks the Web3 potential of smart contracts.
Reverse Gas Model (AKA "canister pays")
In dapps built on Ethereum (as an example), users require a wallet or tokens to use it. This slows down adoption of dapps because using a dapp is not as simple as clicking on a website link; it requires users to buy tokens, install browser plugins, etc. Internet Computer dapps have he "Reverse Gas model" where users can interact with a dapp without having to pay in tokens since the canister can store a certain amount of cycles and pay for the user.
As an example, the Motoko Playground dapp is hosted and executed entirely on-chain and it does not require visitors to pay for the computation: https://m7sm4-2iaaa-aaaab-qabra-cai.raw.ic0.app/
Internet Identity is a blockchain authentication system that enables you to sign in securely and pseudonymously to dapps on the Internet Computer. This makes logging into dapps easy and safe for consumers.