I’m confused about all the different terms for Buddhist meditation, like shamatha, vipassana, zazen, vipashyana, mindfulness, awareness, calm abiding, insight, just sitting, etc. What’s what?
There are nuances in the way different schools approach it, but basic Buddhist meditation comes down to two fundamental practices: concentration and insight. These are also called mindfulness and awareness. Most of the terms you mention are names for one or both of these practices. Buddhist practice always starts with meditations that calm and concentrate the mind, such as following the breath. That’s because an unstable mind that flits from thought to thought and perception to perception cannot take the crucial next step—insight, seeing deeply into the nature of reality.
While many religions practice some form of concentration, insight is Buddhism’s unique specialty. With the stable, focused, and fully present mind you have developed in your mindfulness practice, you investigate the nature of reality. You may discover it is impermanent, has no solid self, and is marked by suffering. These are called the three marks of existence. You could also turn your focus on your mind itself, if we can find such a thing, and investigate its true nature. But it’s better not to think too much about what you might discover, because words, concepts, and hopes will only get in the way of direct experience. The journey of insight is a personal and individual one. We wish you great joy on yours.