What is the balancing item in the balance of payments?

The 'Balance of Payments' of any country is the difference between the money made by exporting goods against money spent on importing goods from overseas.

Take a simple example.... A country sells 100 billion worth of cars to Another Country - BUT - at the same time, imports 20 billion worth of grain. The balance of payments on that single transaction is -80 billion, because the country made more selling the cars than it spent on importing grain.