What are the main types of Buddhist meditation - samatha and vipassana? How are they alike and how do they differ?

Samatha (samatha) is the practice of concentration and calming of the mind; vipassana (vipassanā) is the practice of insight. In the suttas these are two complementary lines of development: samatha develops the mind and helps cling less to habitual sensual pleasures, while vipassana develops wisdom and leads to the ending of ignorance (AN 2.31). Both practices are needed for final liberation (the attainment of Nibbana).

• Samatha techniques (as a rule, various kinds of meditation are meant) gather and settle the mind through concentration on a chosen object - the breath, goodwill, a kasina (a special visual object for meditation, for example a coloured disc, earth, water or fire). As a result the practitioner reaches one-pointedness of mind, a steady sharp focus of attention. That focus then makes it possible to reach the state of utmost concentration - samadhi (samādhi). Within such concentration four levels of absorption are distinguished, the so-called jhanas (jhāna).
• Vipassana observes experience so that its conditioning by the five aggregates of clinging becomes noticeable, along with impermanence (anicca), unsatisfactoriness (dukkha) and not-self (anattā). As a result the practitioner develops wisdom (paññā), which leads to insights into the qualities of perceived experience.

How the two practices are combined is often individual. A developed state of concentration, samadhi, does not by itself lead to insights and Nibbana. At the same time, insight practices also need a sufficiently steady, calm mind. So the question “where to start” is most often settled by temperament and by a teacher. In AN 4.170 Ananda says that all the monks and nuns who declared the attainment of arahantship in his presence had gone one of four ways: samatha before vipassana; vipassana before samatha; the two developed in tandem (yuganaddha); and the case where the mind is first seized by agitation about the Dhamma and then settles, becomes unified and enters samadhi. Mindfulness of breathing, for example, described in MN 118, joins samatha and vipassana. Splitting practice into a “samatha course” and a “vipassana course” is mostly a later and modern way of organising teaching.

Where to read: MN 118, MN 149; on the four routes - AN 4.170, on the pair itself - AN 2.31.