A packet is the document containing the questions used in a particular round at a given tournament. In most tossup-bonus format tournaments, an edited packet consists of 20 tossups and 20 bonuses, followed by one or more tiebreaker tossups and one or more extra bonuses. The collection of all the packets for a given tournament is called a set.
For some reason, quizbowl players in Canada usually say "packs" rather than "packets;" some Canadians make matters even more confusing for American listeners by using the word "packet" to refer to an entire question set. The word "packs" is filtered and automatically replaced with "packets" on the forums.