The Hugo Ceremony is the culminating event of Worldcon. It is held one of the last two night of the convention and is normally the only event at that time.
The Hugo Ceremony is focused on awarding the Hugos (surprise!), but there is normally a bit more than just the bare essentials. The ceremony is presided over by an MC who is the convention's toastmaster if it has one. (Not all Worldcons do.) The MC usually does a schtick of some sort as an introduction and while introducing the presenters. (Modern practice is that the MC does not present the Hugos directly, but provides continuity and presents the individual presenters who each award one or two Hugos.)
In addition to the Hugos (and, of course, the Campbell Award which by the WSFS constitution is handled like a Hugo, the ceremony may present one or more Committee Special Awards. Other awards are sometimes presented or mentioned, though this practice has been declining. (For example, the First Fandom Hall of Fame Award and the Sieun Awards used to be a regular part of the Hugo Ceremony, but are no longer.)
The ceremony typically runs about an hour and a half, but has been known to get out of control and run up to two and a half hours.
Immediately following the end of the Hugo Ceremony, the winners assemble on stage for photos, and the complete Hugo voting statistics (the Hugo voting report and the Hugo nominations report) are made public.
Today's Hugo Ceremony is a descendant of the old Hugo banquet, but a food function has not been a part of the Hugo Ceremony for many decades now.