If any two planets are opposite each other in the zodiac, then they are in Opposition. When any two planes are at 60 degree angles to each other, then they are Sextile, and when they are 120 degrees apart they are Trine. The effect of an aspect between two planets is strongest when the fastest planet reaches the exact angle of the aspect. The interpretation of aspects is based impart on how the planets fall into signs with similar or conflicting elements and qualities. The aspects are no longer described as good or bad, but rather as harmonious or inharmonious.
Harmonious aspects can help matters along.
Neither harmonious or inharmonious, this aspect merges and intensifies the energies of two planets. Inner tension can arise if the planets have conflicting natures. Harmonious aspect that helps energies flow toward attainment of your goals, provided you make some conscious effort to achieve them yourself. It forces you to choose between your conflicting inner needs and urges. This can create such beneficial consequences that things become to easy for you and you become lazy.