Parallels have had their effectiveness proven by Mundane Astrology, even though most astrologers today ignore them.
They occur when two bodies are at the same ecliptic latitude.
They should be avoided, given how little ecliptic latitude varies.
They occur when two bodies are at the same declination (the celestial Equator is the base plane).
They are the best known and still the most neglected. They are considered weaker conjunctions, or a reinforcement of another aspect that already exists.
They occur when a third point or body is at the same distance from two others.
Together with mundane parallels, they are the origin of what is called midpoints.
They occur when a third point or body is at the same distance from one of the axes of the world.
They can occur with the axes: ascendant and descendant, midheaven and imum coeli, and equatorial ascendant and equatorial descendant.
Many authors in Astrology changed the original name of what they found in order to claim authorship of the technique, out of pure vanity. This still happens today.
Zodavia uses and prefers the original nomenclature.
See also Celestial coordinate system