Something described as fructuous is productive or profitable. It can describe an agricultural field that yields a plentiful harvest, or a stock market investment that yields a big profit.
A simpler, more common synonym for fructuous is fruitful. A fructuous apple tree produces a lot of apples, and an apple orchard is fructuous if it yields a nice profit from selling those apples to consumers. On a more metaphorical level, the term might describe a productive partnership, business venture, or even a rewarding college degree. The Latin root fructus, meaning "fruit," was closely tied to enjoying something, so something fructuous is something you can enjoy the results of.