Way back when, grand rounds actually included the presentation of a real, live patient, in the flesh, who was examined and questioned before the audience as an introduction to the topic on which the speaker would expound. In some cases, the patient's diagnosis was not revealed until the end of the hour. Richard Selzer published a quite funny essay about being a student preparing a patient to be presented at Grand Rounds. (Was that in Down From Troy? I don't remember.) This way of doing things has pretty much gone out of fashion.
Grand rounds has become a one hour lecture, generally held once each week (during the academic year or year round) for faculty, housestaff and "whatnots" as well as medical students (in some instances). Each department holds its own Grand Rounds (medical grand rounds, OB/GYN grand rounds, surgical grand rounds, etc). Speakers come from within the department as well as invited guests. Sometimes a "named" lecture is given during grand rounds and the income from an endowment is used to pay the guest speaker's travel expenses and a stipend (sometimes there's a plaque or memento of the occasion). Because the entire department is (or should be) present for grand rounds, it is also an occasion to give teaching awards and other such stuff on a recurring basis.
I'll take that under advisment. 
