There are 4 kinds of bariatric operations (of which a combination is also possible)
Restrictive surgery: Gastric Band and Sleeve Gastrectomy (also hormonal)
Malabsorptive surgery: Scopinaro, Duodenal Switch
Restrictive + malabsorptive + hormonal surgery: Gastric Bypass, Omega Loop Gastric Bypass
Conversional surgery: Band to bypass, Banded bypass, Sleeve to Bypass