Zen meditation, AKA Zazen, is a form of Buddhist meditation, often practiced with the guidance of a teacher which can help show the specific steps and postures. Zen is similar to other mindfulness meditations but may require more discipline and practice.
The goal is to find a comfortable position, focus on breathing, and mindfully observe one’s thoughts without judgment.
In Theravada and Mahayana Buddhism, Zazen is of the Zen tradition. In zazen meditation, you focus on the breath and allow thoughts to come and go. They will subside naturally.
Although this technique is very similar to concentration practices of other traditions, zazen is more structured.
Different traditions have specific postures, mudras of the hands, open/closed eyes, to count breaths, breathing through the nose or mouth.