What the sextile is
A sextile is an angular separation of 60° — one-sixth of the circle. It is a harmonious aspect, generally regarded as an aspect of opportunity: the two planets cooperate easily, offering a talent or an open door. The signs involved always share a compatible pairing (fire–air or earth–water).
Unlike the effortless trine, the sextile asks for a little initiative — the door is open, but someone has to walk through it.
How the sextile works
The sextile brings the two planets into supportive, stimulating contact. It grants aptitude and the possibility of easy exchange between the functions involved, but its gifts are potential rather than automatic. A person may not even notice their sextiles until they consciously engage them; used, they become reliable strengths.
By transit and synastry
By transit, a sextile offers a window of opportunity — a favourable but not compelling moment to act in the relevant area. In synastry it shows where two people can help and stimulate each other with little friction. It is a "minor benefic" among the aspects: helpful, but quiet.