An agenda is a list of items to be discussed or actions to be taken at a meeting or some other form of formal or, at least, somewhat formal human interaction. Just to be clear, formal dress is not necessarily required. By formal, I simply mean that it involves some planning and something that vaguely passes as organization.
I’ve been self-employed for well over two decades now and, in that time, I have, to my great bliss, been able to keep the number of business meetings I’ve had to attend down to a very small number.
Thus, I don’t have a lot of recent experience with business meeting agendas. However, my recollection is that the primary purpose of a business meeting agenda is to let you know in advance how your time will be wasted at the meeting.
Because always knowing exactly how your time is going to be wasted can get boring, to add a spark of the unknown, meetings often go off on wild tangents, ignoring the agenda well before completing it, thereby adding some mystery to the question of how your time will be wasted.