The trine in a birth chart is a point of ease, or harmony. It's where natural flow exists, and can be easily developed further. Perhaps, as some karmic astrologers say, it's a reward you've earned from a past life!
It is an asset, but can be taken for granted and not fully utilized. The trine is often between planets of the same element (fire, earth, air and water). But it can also be between planets in different signs. The orb is up to 8 degrees for a wide orb, but more potent at 5 and under.
Transiting planets also form aspects, including the trine. You can be "preparation awaiting opportunity," when you know a supportive trine is coming to draw out the potential of a natal planet. This is a practical way to look ahead and make the most of cosmic forces.