Erythritol is a natural sugar subsitute which occurs naturally in fruits and mushrooms. It is up to 70% sweet as normal sugar but has virtually no calories, very low on carbs, does not affect your blood sugar, has a low GI index and does not cause tooth decay. It looks like the normal granulated stuff though.
It is absorbed by the body into the blood but then is excreted out into the urine, and is therefore unlikely to cause gastric side effect like other sugar substitutes. However, I must point out that it is not suitable for irritable bowel sufferers. You can use erythritol in place of sugar for all your baking. It works just as good as normal sugar. It actually looks like sugar and when I purchase it I often cheekily think to myself, they could be selling me normal sugar at twice the price....I will sometimes grind mine down into a powder with a hand processor to use in cooking. It will look like icing sugar and is easily to dissolve in some recipes.