What is the significance of the "rule of 15" in bridge bidding strategy?

The "rule of 15" in bridge bidding strategy is a guideline used to determine whether a hand is suitable for opening the bidding. It suggests that if the sum of the number of high card points in a hand and the length of the longest suit is at least 15, then the hand is strong enough to open the bidding. This helps players make informed decisions about when to bid and when to pass, ultimately improving their chances of success in the game.