On-chain Metadata is stored in Blockchain. So Metadata is trusted and the Metadata will live forever in the blockchain
Off-Chain Metadata is stored in 3rd party servers. We have to trust the 3rd party for data protection. If the 3rd party goes down your NFA is gone. you will be left with a unique token (NFT)
So please be careful when you buy long term assets like ARTs. Buy NFT Assets Minted on On-Chain Minting Platform
Next Question: Risk in Nft Assets?.