The surrender bet is similar to the insurance bet you will find in some variations of blackjack. It protects you if the ball lands on the 0 or 00 green segments. When this happens, you will receive half your bets back. This actually reduces the house edge somewhat and makes American Roulette more attractive to play. This only happens on American Roulette tables that offer the Surrender rule, so check if it does first. Many tables will not offer this rule.