The strongest influence in Astrology is the aspects (mundane aspects above all).
Aspects are angles formed between points in the chart, whether planets, sensitive points such as the ascendant and the midheaven, fixed stars and so on.
There are two kinds of aspect: mundane aspects and zodiacal aspects. Although most astrologers know only coordinates based on the ecliptic, the most powerful influence comes from equatorial coordinates, which take the rotation of the Earth as their main system.
For more on mundane aspects, see the site of the ABA - Brazilian Association of Astrology (in Portuguese).
Aspects are divided between good and bad, harmonious and disharmonious.
Trines and sextiles are harmonious aspects, where the points they connect flow in harmony and bring talents and natural ease, which is why they are considered good aspects, for their fluidity.
Oppositions and squares are disharmonious aspects, where the points they connect carry an excess of the same energy the good aspect has, and precisely because of that excess they produce harmful effects. That is why they are considered bad aspects: the excess of that energy, without fluidity.
Conjunctions, parallels and contraparallels are ambiguous in nature. They bring the good and the bad.
In the charts shown on Zodavia they are drawn in orange, as a colour of caution.
Below are the main aspects of greatest influence that we use.