What's the difference between gastric bypass and lap band?

Big difference: Gastric bypass surgery is performed by surgically cutting away a portion of your stomach so food can no longer get to most of your stomach & leaving a very small portion of stomach that is now reconnected to a portion of the small intestine. Lap band us the placement of an inflatable collar around the stomach making it smaller but not cutting & rerouting the stomach.

Lots: Bypass involves cutting the stomach and re arranging the guts. A band is simply put around the stomach. See a weight loss surgeon for details and diagrams as well as risks and benefits.