Baby rice cereal is one of the first foods often given to a baby when he is weaned off the breast or bottle. It is easy to digest and has no lumps.
You can purchase prepared packets of baby rice that just need mixing with your baby's milk or boiled water, but do make sure they are gluten free if your baby is under 6 months, or has tested positive for celiac disease. You are normally safe with the plain rice, but if flavors have been added, do check the ingredients carefully.
It may work out more economical to buy a large packet of ground rice, and use it for many different purposes, including gluten free baby food and many baked goods. However, do note that it isn't pre-cooked and it won't have the added vitamins and minerals that are in baby rice cereal.