Buying group
A buying group is everyone on the client side who influences a purchase decision — in B2B usually six to ten people, not just the person you spoke to.
A B2B purchase decision rarely belongs to one person. A typical group includes the person who will use the solution, whoever owns the budget, someone assessing risk — legal, technical or security — and often procurement. Gartner's research puts the usual size at six to ten stakeholders.
The practical consequence is specific: the material you send will reach people who were not on your call and have none of the context. The proposal has to rebuild that context by itself, because nobody is going to phone you to ask.
See also
Proposals turns a call transcript into a proposal published as a web page, and shows which sections the client read.