parallels & contraparallels
A planet’s declination is its position in northern or southern relation to the celestial equator. Declinations add another layer to the natal chart, beyond the Zodiac wheel / ecliptic, and come with their own two major aspects: the parallel and contraparallel. These aspects are virtually identical to conjunctions and oppositions both in energy and calculation, except they exist on the north-south axis (above/below celestial equator) instead of along the east-west (Zodiac).
A contraparallel takes place between two planets whose declinations are at approximately the same degree on different sides, one north and one south, whereas a parallel takes place between two planets whose declinations are at approximately the same degree on the same side, both north or both south.
To locate the parallels & contraparallels in your natal chart, you can use the chart calculator on astro-charts.com (select “Show Declinations” in settings).
The reason a 1° orb is used for declination aspects is because they present themselves on a much more limited plane than Zodiac aspects; the former only has a range of 47 degrees, while the latter has 360 degrees, where orbs of up to 10° are realistic and usually necessary. Contra/parallels are naturally extremely potent, within such a small field of variation, so in order to gain any meaningful insight from their presence, it’s crucial to keep the standards high. If the orb was increased to, say, 3°, you may find that every planet is in a contra/parallel in one’s natal chart. It’s obvious how & why that becomes inapplicable.
Most astrologers interpret parallels & contraparallels in the same way you would a conjunction or opposition aspect between planets in the Zodiac, and that’s valid, but it’s important to note that the meaning of conjunctions & oppositions is based in the relationships between archetypes, while contra/parallels are free of Zodiac influence -- they focus completely on the planets themselves. Because of this, you may have (for example) a contraparallel in a pair of signs which border each other in the Zodiac. It’s important to synthesize your declination aspects with the rest of your natal chart to offer context for their contact. In addition, it’s also helpful to recognize that when separate from the Zodiac (which represents the 12 fundamental manifestations of human consciousness), the planets aren’t as personal; they become less like forces of personality and more like forces of circumstance or reality. For this reason, sometimes parallels & contraparallels are not expressed as intensely in a person as they are in their life story / the themes of their experience (though they still may have strong impact on either).