Fodmaps are sugars and sugar alcohols that many people struggle to process well. Lactose intolerance is commonly known but there are lots of others. Wheat fructans are in most gluten containing foods and may be why some people find gluten free diets beneficial even if not coeliac.
Yeah and you can systematically work through the various FODMAPs to figure out which ones cause you problems. It's not that FODMAPs are all bad, it's that there are groups of foods that you might be sensitive to.