LedgerKey holds information to identify a specific ledgerEntry. It is a union that can be any one of the LedgerEntryTypes (ACCOUNT, TRUSTLINE, OFFER, DATA, or CLAIMABLE_BALANCE). Search for LedgerKey in stellar-ledger-entries.x for more information.
OperationID is a union with one possible type (ENVELOPE_TYPE_OP_ID). It contains the transaction source account, sequence number, and the operation index of the CreateClaimableBalance operation in the transaction. Search for OperationID in stellar-transactions.x for more information.
ClaimableBalanceID is a union with one possible type (CLAIMABLE_BALANCE_ID_TYPE_V0). It contains a SHA-256 hash of the OperationID for Claimable Balances.