The angle and the element it shares
A trine is a third of the zodiac, a hundred and twenty degrees, and the orb used here is seven. Trines join signs of the same element, so a Moon in Cancer trines a Venus in Scorpio or Pisces, and a Moon in Gemini trines a Venus in Libra or Aquarius. That shared element is the whole mechanism. The two bodies are speaking the same language and neither has to translate.
In the sky the Moon makes two trines to Venus in each lunar cycle, one on each side of the opposition. The aspect is therefore common, and no conclusion should be drawn from having it beyond what the signs and houses say.
A trine that crosses a sign boundary, say a Moon at twenty nine degrees of Taurus to a Venus at three degrees of Libra, is out of element and should be read as a much weaker version of the same thing, if at all.
Need and taste in agreement
The Moon signifies the automatic layer: comfort, habit, what you do without deciding. Venus signifies value: attraction, judgement about what is worth having, the manner in which you make things pleasant. A trine means those two agree by default. What settles you is also what you find attractive, and what you find attractive is also what settles you.
The usual descriptions follow from that. Sociability that costs no effort, a settled sense of taste, an ability to make a room comfortable without thinking about it. People with the aspect often do not notice it, because nothing in their experience has ever drawn attention to the pairing.
The counterweight the older literature insists on is that undeveloped talent is still undeveloped. A square makes you work on the same pairing whether you want to or not. A trine only offers, and a person can go a long way without ever taking it up. That is the standard caution about the aspect and it is worth more than the compliments.
What sign and house do to it
Element sets the flavour completely. In water signs the aspect is read as emotional attunement and a tendency to absorb the mood of a room. In earth it becomes practical: comfort with a physical form, an eye for materials and a preference for arrangements that last. In air it turns social and verbal, in fire it becomes warmth and display.
House placement decides where the ease shows. A fifth house Venus trine an eleventh house Moon looks like a life with easy company in it. A sixth house Venus trine a second house Moon shows up as a pleasant working life and an unfussy relationship with money. The ease is real in both cases, but it is applied to entirely different material, which is why generic trine descriptions read as flattery.
Orb, retrogrades and reading yours
Trines hold their character across a wider orb than squares do, but the same rule applies. Inside three degrees the aspect is a visible feature. At six or seven it is a mild disposition. Since the Moon covers about thirteen degrees a day, a shaky birth time can move a trine in or out of orb, so the recorded time is worth confirming before leaning on it.
A retrograde Venus is read as turning its judgement inward and reviewing it, so the trine still flows but tends to be described as private rather than social. Venus at a station, barely moving, is read as more emphatic than a Venus at full speed.
The widget above gives you the separation in degrees, both signs, both houses and the applying or separating direction, which is what decides whether the general description above is worth applying to you at all.
Questions people ask about this
What does Moon trine Venus mean?
It means the two bodies were a hundred and twenty degrees apart at birth, within seven degrees of orb, usually in signs of the same element. The tradition reads it as instinct and taste agreeing without effort.
Is a trine automatically a good aspect?
Astrologers describe it as easy rather than good. The standard caution is that an ability which was never tested is easy to leave undeveloped, so the aspect is read as an offer rather than an achievement.
Do both bodies have to be in the same element?
In the clean version of the aspect, yes. A trine that crosses a sign boundary breaks the element match and is generally read as a diluted version, or set aside entirely by astrologers who work by sign rather than by degree.
How often does this occur?
The Moon makes two trines to Venus in every lunar cycle, so it is one of the ordinary aspects and appears in charts at a common rate. Its frequency says nothing about its strength in an individual chart.
What weakens a trine?
A wide orb, a crossed sign boundary, or a hard aspect from another body to one of the two ends. A Venus trine the Moon but squared by Saturn is read very differently from the same trine standing alone.
Which is more informative, this or the square?
Neither is more informative in principle. The square tends to be more noticeable to the person concerned because it demands a response, while the trine is often only recognised once someone points it out.