What Venus governs
Venus covers attraction, taste, money, and the terms on which someone is willing to exchange one thing for another. The romantic reading is the best known but it is a subset. The same placement shows what a person spends on, what they find beautiful, and how much they will concede to keep a relationship comfortable.
It also describes the manner of approach rather than the object of it. Venus in Capricorn approaches slowly and with conditions; Venus in Aries approaches directly and loses interest when the pursuit ends. Neither says anything about who is eventually chosen.
Within forty-seven degrees of the Sun
Venus never appears more than about forty-seven degrees from the Sun, so it can only fall in the solar sign or within two signs either side of it. Someone with the Sun in Aries can hold Venus anywhere from Aquarius to Gemini and nowhere else. This is why some sign combinations that appear in horoscope writing are astronomically impossible.
The aspect range is limited in the same way. Venus can conjunct the Sun and form a semi-sextile or a sextile with it, but never a square, a trine or an opposition.
Speed and dignity
Venus spends about three to four weeks in a sign at ordinary speed, so the placement is personal and shared with people born within roughly a month. It rules Taurus and Libra, one earth sign and one air sign, which is why its reading splits between physical enjoyment and social negotiation.
Venus is exalted in Pisces, in detriment in Aries and Scorpio, and in fall in Virgo. The fall in Virgo is about the habit of assessing and correcting, which is useful work and awkward company for a body whose function is acceptance.
Retrograde, which is rare
Venus turns retrograde about every eighteen months and stays that way for around six weeks, which makes it the least frequent retrograde among the personal planets. Something in the order of one person in twelve or so is born during one, so it is uncommon without being unusual.
It is read as a reconsideration of what is valued rather than as an obstruction. In practice that often shows as attraction to things outside the conventions the person grew up with, and as a slower or more revisited approach to committing.
Why the house decides the reading
The sign gives the manner and the house gives the arena. Venus in the seventh house puts the emphasis on partnership; the same Venus in the second puts it on income and possessions; in the tenth it attaches to reputation and the work someone is publicly known for. These are different lives, and the only thing separating them in the chart is the birth time.
Without a time, the sign and the aspects are still readable. The house is not, and it is worth saying so rather than offering a guess.
Questions people ask about this
How far can Venus be from my Sun sign?
About forty-seven degrees, which means the solar sign or up to two signs either side of it.
How often is Venus retrograde?
Roughly every eighteen months, for about six weeks. It is the rarest retrograde among the personal planets.
What are Venus's dignities?
It rules Taurus and Libra, is exalted in Pisces, in detriment in Aries and Scorpio, and in fall in Virgo.
Does Venus show who I will end up with?
No. It describes what attracts you and the terms you offer, not an outcome or a person.