1. This is the number of tricks above the book (six tricks) that a player names in the bidding. For example, bids of 2♣ or 2♦ are bids at the two level, while contracts of 5♥ or 5♠ are contracts at the five level.
2. A way of categorising which conventions are legal in a particular type of competition, with the more complex conventions only allowed in higher-level competitions.