Triphala is not one herb but three, and the proportion matters as much as the ingredients. Amalaki, Bibhitaki and Haritaki are dried, powdered and combined — classically in equal parts — to make what is probably the most widely used formulation in Ayurveda. Each fruit is associated with one of the three doshas, which is why the combination is described as tridoshic: suitable, in principle, across constitutions.
What people notice first is its effect on digestion and regularity. Classical texts describe Triphala as a mild, non-habit-forming support for the bowel, and this is the reason it is taken at night rather than with meals — the intention is that it works while the body is at rest. Taken over a long period it is regarded as rasayana, a rejuvenative, rather than something you reach for once and stop.
The taste is the part nobody prepares you for. Triphala carries five of the six tastes, missing only salt, and the dominant impression is sour and astringent. That astringency is not a flaw in the preparation; it is characteristic of Haritaki in particular, and it is part of how the formulation is understood to work.
The usual form is a half to one teaspoon of the powder in warm water, left to steep briefly, taken at bedtime. Tablets exist and are easier to take, though the traditional view is that the taste is part of the medicine — the tongue registers it, and digestion begins there.
As with any long-term preparation, it is worth taking Triphala under guidance rather than indefinitely on your own. It is not appropriate during pregnancy, and if you are taking prescribed medication the timing relative to those doses is something to discuss with your physician.