What is significator ?

A planet may be taken as a significator of a person or of an event, or of affairs ruled by a House. Its strength by virtue of its Sign and House position and its relationship by aspects are then consulted in arriving at a judgment concerning a desired condition. 

In general the strongest planet in the Figure, usually the ruler of the Ascendant, is taken as the Significator of the native. Similarly the Ruler of the Sign on the cusp of the Second House is taken as the Significator of wealth, of the Seventh House of the partner, of the Eighth of the partner's wealth, and so on. Sepharial speaks of the Sun, Moon, Ascendant and Midheaven as Significators, but Alan Leo prefers to speak of them as Moderators, and includes Fortuna. 

The Sun and Midheaven are by some authorities deemed to have affinity as Significators of the honor, credit, and standing of the subject of the Figure, or of the surviving male head of the family; the Moon and Ascendant to have affinity as Significators of the personal fortunes, changes and accidents befalling the native; Mercury, of his learning, intellectual accomplishments or business acumen; Venus, of his love-affairs, social arts and accomplishments; Mars, of strikes, contentions, enterprises and risks; Jupiter, of wealth and increase; and Saturn, of disease, loss, death and decay. In this use there is danger of confusing the distinction between a Significator, as representing persons in Horary Astrology, and Promittors as representative of things promised or desired; but every planet in the Figure can be taken not only as the significator of something, but also as the Promittor of something.