The aspects are the angles the planets make to each other in the horoscope, and also to the Ascendant, Mid-heaven, Descendant and Nadir. The aspects are measured by the angular distance along the ecliptic in degrees and minutes of celestial longitude between two points, as viewed from the earth.
They indicate focal points in the horoscope where the energies involved are given extra emphasis. The more exact the angle, the more powerful the aspect, although an allowance of a few degrees each side of the aspect called an orb is allowed for interpretation.
According to astrological tradition, they indicate the timing of transitions and developmental changes in the lives of people and affairs relative to the Earth.