Ledger: the heart of the core, this is the immutable list of the transactions that have been processed by the core, often regarded as the source of truth for movement of funds in the bank

Accounts: the core account record that might map to a customer account but equally could map to a bank owned account or a special accounting record such as a nostro or wash account. Each transaction in the ledger references both a debit and a credit account

Balances: the core computes balances across all of it’s accounts. Depending on the complexity of the core, this can range from a simple balance for each account, to a more involved structure that tracks multiple dimensions within each account, such as asset, currency and ring-fenced funds

Product engine: a broad term to encapsulate any ‘product’ decisioning the core might make around an account. The simplest case is deciding if any given transaction is allowed to be added to the ledger, which would typically involve a balance check. The scope of the product engine differs from core to core and can involve anything from interest calculations to sweeping funds across accounts to meet complex processing rules.