Sporran has off-chain & on-chain DIDs. What does that mean?

Off-chain DIDs are not written to the blockchain and are not as flexible as on-chain DIDs. They require the user to manually download their credentials when issued and imported when restoring a wallet from seed phrase. In addition, off-chain or “light” DIDs are not able to rotate their keys or sign messages via Sporran. 

On-chain DIDs are published to the blockchain, which means the user does not need to manually manage them and their hashes can be read. In addition, on-chain DIDs can rotate their keys and sign messages via Sporran.