An aspect is the precise distance between any two points in a horoscope. Usually aspects are formed between two planets, although aspects between any one planet and the angles (Ascendant, Descendant, MC and IC) are also considered. The more exact that an aspect is, the more important it is said to be according to astrological precedent and tradition. The difference between the exact aspect and the actual aspect is called the orb. The astrological aspects are noted in the central circle of the natal chart, where the different colors and symbols distinguish between the different aspects.

The aspects are used to establish how the planets combine to stimulate and moderate each other's influence. They are divided into two categories, major or minor, and harmonious or tense. Generally, major aspects are much more powerful than the minor; but there are certain astrologers who place a greater than usual emphasis upon the minor aspects.

The tense aspects cause friction between the planets involved. This friction brings difficulties and problems, which may be psychological, environmental or a combination of the two. In coping with these problems many people experience failure, but some will be driven to overcome their difficulties and in the process develop their astrological potential. The harmonious aspects bring an easy relationship between the planets involved. They provide a helpful environment for innate abilities which the individual may take for granted, but fail to develop fully.

Each type of aspect, therefore, has two faces. The tense aspects bring difficulties which can result in great achievement, while the harmonious aspects bring easy conditions which can lead to wasted opportunities. It is preferable to have a balance of tense and harmonious aspects. Individuals with only harmonious aspects may have plenty of potential but no drive to develop it, while those with only tense aspects may lack the faith and optimism to overcome difficulties.