Tangyak, the decoction
Several herbal materials are tied into one packet, simmered in water for a long time, and the liquid is strained off and drunk. These days the clinic simmers it and packs it in single pouches. You are told whether to drink it before or after a meal, and you take several days' worth at once. You can ask for the prescription sheet listing the materials and amounts.
Korean medicine rarely uses one material alone. It works in formulas - several materials tied together in set proportions. The simmering time and the strength of the flame belong to the formula too, so some materials go in first and others near the end. The names and the make-up of the formulas carry on from what old medical books, the Donguibogam among them, set down. That is what the discipline writes in its own words, and we write nothing beyond it.
This note is not a consultation. Tell the doctor exactly what other medicine you take. Do not drink a decoction prescribed for someone else.