A pill bug, or woodlouse, is a small bug that appears to have an armored shell and can roll into a ball when threatened, much like an armadillo. They are usually under an inch long, and feed mainly on decaying plant matter, presenting no threat to humans. They are sometimes prone to consume live plants, including agricultural crops, which makes them a nuisance to crop owners.
Pill bugs are harmless and are even kept as pets in some areas. They sometimes occur in exceptionally large numbers however, which can lead to the view that they are pests. If you are finding them in your home, it is best to try and remove moisture and clean up any areas they may be using to shelter. Pillbugs like water sources and dark spaces, so removing those elements will help discourage their presence.