The public key is used to verify the account's signatures. It is stored on the blockchain with the first-issued transaction. An account which has not issued any transaction has its public key field empty.

The height at which the first transaction was issued.

The importance score determines the probability of an account to harvest the next block in case the account has harvesting turned on and all other accounts are harvesting too.

The vested balance represents the amount of XEM in an account that has matured over time and is eligible for harvesting. The vested balance is used to calculate the account’s importance score for harvesting purposes.