、。
Trade consists of the two-way flow of goods — that is, exports and imports.
Literal
Trade [topic-は] goods [of-の] two-direction [of-の] flow, namely export [and-と] import [from-から] is-composed.
すなわち ('namely, that is') is a formal explanatory connector typical of academic and legal writing — much weightier than つまり in casual speech. 両方向 ('two directions, both directions') and 流れ ('flow, current') give the definition a precise, almost diagrammatic feel. からなる ('to be composed of, consist of') is a set written-register pattern. Reads like a passage from an economics textbook.