A brochure may give the main procedure a whole page and leave preparation in a footnote. In descriptions of Panchakarma, purvakarma means measures that precede a principal intervention. Snehana, associated with oils or fats, and swedana, associated with induced sweating, often appear here.
Preparation sounds mild in English. The word says where something falls in a sequence; it does not tell you how demanding the intervention is. Oil applied to skin and a substance taken internally involve different exposures. A warm room and an intensive heat procedure are different experiences even when both are described as warming.
Before agreeing, ask for a plain-language account of what will happen, who will supervise and when the plan would be stopped. Do not begin taking oils or restricting food simply because an itinerary calls the first day preparation. A decision about the main procedure does not remove your right to ask about the steps before it.
Further reading: Panchakarma terminology (Ministry of Ayush annual report) · Detox and cleanse claims (NCCIH)