A buying committee is a group of people within a company who take part in a purchasing decision. It typically includes the user who will work with the solution, a specialist assessing the technical side, a finance person or buyer tracking price and terms, an approver with budget authority, and sometimes also the legal or security department. Each has different concerns and different criteria, so a single presentation is not enough. The salesperson needs to find out who all is involved in the decision, whom they have not yet met, and who within the organisation is championing the purchase. It is precisely this internal champion who needs to be given materials with which to defend the solution to colleagues at the moment when the salesperson is not in the room. The most common cause of lost deals in B2B is not competition, but the decision to do nothing.
See also: Brand in B2B, Sales materials, Reasons for Losing a Deal.