Nissen fundoplication is a surgical procedure used to treat severe acid reflux. 
During the surgery, the upper part of the stomach is wrapped around the lower end of the oesophagus (the tube that carries food from the mouth to the stomach). This creates a barrier that helps prevent stomach acid from flowing back into the oesophagus, reducing symptoms like heartburn and regurgitation. 

The surgery is often done laparoscopically, using small incisions, which means recovery is usually faster and less painful compared to open surgery.

Gastric bypass surgery is a type of weight-loss surgery designed to help people lose weight when diet and exercise alone haven’t worked, or when weight-related health problems are severe.

A sleeve gastrectomy is a type of weight loss surgery where a large part of the stomach is removed, leaving behind a small, tube-shaped "sleeve."
This smaller stomach holds less food, helping you feel full faster and eat less overall. It also affects your hunger hormones, so many people feel less hungry after surgery.