In astrological tradition, the Venus governs love, beauty, values, and what is found pleasurable, while Capricorn is a earth sign read as ambitious, disciplined, responsible, and long-game minded.
So Venus in Capricorn is often read as a placement where how affection is given and what feels worth having takes on a ambitious, disciplined quality. Tradition holds that someone with this placement tends to draws toward connection and harmony in a way that feels responsible — coloured by the earth-sign temperament of Capricorn rather than by any single rule.
None of this is a prediction or a fixed trait. These are tendencies astrologers have long associated with Venus in Capricorn, and how they actually show up depends on the rest of the chart — the houses, the aspects, and the other placements that this guide cannot see.
A general guide to astrological tradition — tendencies, not predictions. It describes the placement in the abstract and is not about any specific person.