The geometry and the phase
A trine is a hundred and twenty degree separation with an orb of about seven for these two bodies. The Moon makes two trines to the Sun in every lunar cycle, one waxing at roughly the gibbous stage and one waning, so like the square this is a doubled window and therefore common.
The two bodies land in signs of the same element. Fire trines fire, earth trines earth, and so on. That shared element is the entire mechanism of the aspect in traditional terms, since two bodies in the same element are held to want compatible things without having to negotiate.
The Moon crosses the seven degree window in around a day, so the phase is not something you would notice by looking at the sky unless you were counting. Roughly a fifth of the lunar month sits inside one trine or the other.
What ease actually means here
The Sun is deliberate direction and the Moon is habit. A trine between them means the habit already supports the direction. You are not fighting your own reflexes to do what you set out to do, and the effort other people spend on self-management is available to you for something else.
The standard caution is that nothing here demands anything. Squares and oppositions produce pressure and pressure produces development. A trine produces a facility, and a facility that is never tested tends to stay at whatever level it reached on its own. Astrologers describe this as talent going unnoticed by its owner, because it never felt like an achievement.
So the useful reading of a Sun trine Moon is comparative. Look at the rest of the chart for the aspect that does make demands, and treat the trine as the resource that gets spent on it. A chart with a strong square somewhere else and this trine in the background is a very different proposition from a chart where the trine is the only significant contact between the lights.
Element and house give it a subject
The shared element sets the tone. A fire trine between the lights reads as confidence that arrives before evidence. Earth reads as steadiness and a low tolerance for the impractical. Air reads as an easy match between what you think and what you feel about it. Water reads as instinct that seldom argues with intention.
The houses then say where the ease shows up. Both lights in succedent houses, the second, fifth, eighth or eleventh, tends to look like durable resources. Both in angular houses is far more visible from outside. A trine between a twelfth house Sun and a fourth house Moon may never be apparent to anyone but the person concerned.
Orb and the honest limits
Tight trines, inside two or three degrees, do read the way the descriptions claim. Wide ones are weak, and a trine at six or seven degrees that also crosses a sign boundary has lost the shared element that gave it meaning, which is the case where the textbook reading simply fails.
Be careful with claims made for this aspect. It is often written up as a guarantee of a happy temperament or good relations at home, and that goes well past what the geometry supports. A trine describes an absence of internal obstruction between two bodies. It does not describe circumstances, and it says nothing on its own about the rest of the chart.
The check above gives you the separation in degrees and both sign positions, so you can see whether your trine is the tight in element kind or the wide out of element kind that most general descriptions quietly assume away.
Questions people ask about this
How common is Sun trine Moon?
Fairly common. The Moon trines the Sun twice in each lunar cycle and the seven degree orb keeps each window open for about a day, so a meaningful share of births fall inside one of the two.
Is a trine always a good thing?
Not automatically. The tradition reads it as ease rather than benefit, and ease with no demand attached to it often goes unused. A trine is best judged next to whatever in the chart is actually applying pressure.
Are my Sun and Moon in the same element?
With a clean trine, yes, both bodies sit in fire, earth, air or water signs of the same element. A wide trine can slip across a sign boundary and break that, and when it does the classic interpretation stops applying cleanly.
What moon phase does a trine correspond to?
Roughly the gibbous stages, waxing or waning, when the Moon is a third of the zodiac from the Sun. It is not a phase with a common name, so it is easier to identify from a chart than from the sky.
Does the waxing or waning trine differ?
Only for astrologers who read lunar phase closely. The waxing trine is treated as ease in building something, the waning as ease in consolidating it. The hundred and twenty degree angle itself is the same either way.
How tight does the orb need to be?
Inside three degrees it is a clear feature. Beyond five it is faint, and beyond seven most astrologers do not count it at all. The exact figure for your chart is in the check above.