The balance of payments accounts summarize payments made to or received from foreign countries. Receipts are considered credit transactions while payments are considered debit transactions. The balance of payments is a function of three components: transactions involving export or import of goods and services form the current account, transactions involving purchase or sale of financial assets form the financial account, and transactions involving unconventional transfers of wealth form the capital account. The current account summarizes three variables: the trade balance, net factor income from abroad, and net unilateral transfers. The financial account summarizes the value of exports versus imports of assets, and the capital account summarizes the value of asset transfers received net of transfers given. The capital account also includes the official reserve account, which summarizes central banks' purchases and sales of domestic currency, foreign exchange, gold, and SDRs for purposes of maintaining or utilizing bank reserves.