Conjunction - Semi-Sextile - Octile - Sextile - Quintile
Square - Trine - Tri-Octile - Quincunx - Opposition
The profile for each aspect lists the common name(s) of the aspect, its symbol, the angle between the planets (in degrees), the orb (in degrees), the family of aspects it belongs to, and some keywords and notes that describe the nuances of this connection.
(There's a lovely Italian Translation of this page if you'd like to see it...)
When two planets are certain angular distances apart as measured along the ecliptic, they are said to be "in aspect" to each other. Aspects serve to combine the energies of the individual planets into larger and more complicated groups, forming connections between different parts of the personality. When a large number of planets are combined in this way, they form a "planetary complex". Such complexes are normally potent forces shaping one's personality and behavior.
Not all aspects are equally adept at combining two planets. In some cases, this actually results in conflict or disharmony. Each angle has its own personality or way of expressing the relationship between planets. This comes across as distinct "moods" or types of experience. Further, aspects tend to fall into "families" (based on harmonics and notions of cyclic time) that group them into similar influences.
Aspects don't have to be exact to be effective, although the effect is strongest when the planets are the precise angular distance apart mentioned below. There is a leeway or "margin of error" allowed when calculating aspects that is called the "orb". When the planets move within orb of the exact angle, the aspect kicks in and begins to build in strength, reaching maximum influence at exactitude. As the planets separate, the influence decreases, disappearing as they slip out of orb.
Angle: 0 / Orb: 9 / Family: none
This is the most direct and powerful connection between two planets, since they are in the same place in the zodiac. Highly variable in influence, very dependent on the natures of the planets involved. The start of new cycles of experience, new beginnings. Very instinctive, unconscious combining (or identification) of two parts of the psyche, often unexamined or unnoticed.
Angle: 30 / Orb: 4 / Family: 3
A generally positive and constructive aspect, although it tends to combine planets in incompatible signs, making the connections somewhat "forced". Can therefore lead to frustrating difficulties or needing to make "no win" choices. The problems are usually subliminal.
Angle: 45 / Orb: 4 / Family: 2
Agitation, difficulty, stressful. One's efforts are stifled by surrounding circumstances (often impersonal). These problems are meant to show the weaknesses in the original way the planets are working together.
Angle: 60 / Orb: 6 / Family: 3
Very positive, optimistic, constructive. Progress is not automatic, but requires the person to make an effort. Generally works out exceptionally well, unless one fails to seize the opportunity. Easy-flowing connection.
Angle: 72 / Orb: 4 / Family: 5
The strongest of the 5-family aspects (there are others not listed here). A combination that stresses creative approaches to overcoming problems, the use of intellect and imagination to transcend old limitations. Quirky in nature, not really fitting "good/bad" categories.
Angle: 90 / Orb: 9 / Family: 2
Conflict, stressful, difficult. One's plans seem to be at cross-purposes with others, leading to conflict and disagreement. A very trying, uneasy combination; plans must be proved and modified. Tension, resistance. The planets in a square often describe parts of the personality that are at odds with each other. The biggest "bogeyman" of all the aspects.
Angle: 120 / Orb: 9 / Family: 3
Easy-going (too much so!), constructive, flowing, helpful. Tends to laziness or taking things for granted. Balance, harmony, rest, passive receptivity. Can fall into old patterns of behavior and ruts, mostly due to lack of awareness; difficult to break out (unless there are some challenging aspects to help). Relies on "dumb luck", letting things work out spontaneously (it usually works).
Angle: 135 / Orb: 4 / Family: 2
Difficult, stressful, agitated. Conflicts with others, though rarely directly or openly. These planets tend to work at cross-purposes, creating discord. More annoying and frustrating than truly difficult (unlike the square).
Angle: 150 / Orb: 4 / Family: 3
A mixed influence, mostly difficult. Combines planets in incompatible signs, making for a "forced" or uneasy mix. Causes trouble with others (especially when an inequality of status exists). Subtle frustrations in everyday life.
Angle: 180 / Orb: 9 / Family: 2
Conflict between two polar opposite forces, head-to-head disagreement. Dealing with one's opposite, however, leads to greater awareness of how these poles operate within you. This aspect works by the process of projection, of seeing hidden parts of one's psyche "out there" in the world. Challenging aspect, but it can lead to better self-awareness.