What to the manual posting options mean?

Liability invoice: Generates an open liability (creditor) that can be closed again via the bank reconciliation.

Liability payment: Settles an open liability (creditor) that was posted through the posting workflow.

Receivable invoice: Generates an open receivable (debtor) that can be closed again via the bank reconciliation.

Receivable payment: Settles an open receivable (debtor) that was posted through the posting workflow.

General ledger: All other postings that do not concern either open receivables or open liabilities.