the.com/balance of trade

means The difference in value between what a country sells to other countries and what it buys from them over a given period.

from From 'balance' in its old merchant-ledger sense — the weighing-scale metaphor for comparing two columns of figures until they tip one way or the other — joined to 'trade,' from a Germanic root meaning 'track' or 'course,' as in the path goods travel between buyer and seller. The phrase itself crystallized in the language of 17th–18th century mercantilist economics, when nations literally tallied exports against imports like a merchant tallying debits and credits, anxious to see which side of the scale sank lower.