The bottom of a baby is sensitive, which is why baby wash cloths exist and people don't just use regular wash cloths to wipe their infants as that might cause harm and irritation on the sensitive skin. They differ from regular cloth by both being more absorbent, comfortable, and stronger along with being soft when wet. With how fragile babies can be, it is important to make sure they are clean and taken well care of, as they can easily fall sick or get hurt and as such hygiene becomes extremely important. You often must get more than one, since you'll need to wash them often and switch between the other cloths and making sure there's no filth left on it when you need to use it again. You'll often see them used within hospitals to be used for cleaning the new-born.
Different ways of cleaning babies
Outside of baby wash cloths, tissues and wipes are common sights, being one time use which is good if you're a bit lazy and don't want to wash after each time you use it. Obviously, the cloth is the least expensive in the long run, but sometimes you want to be lazy and not having to deal with cleaning it all the time. Still, using the reusable option is better for the wallet as well as nature, especially if you chose the ones that are manufactured with the goal of taking as little toll on the environment as possible. Regardless, they're an essential for any parent out there.