Peano numbers are a way of counting from one to infinity. They start with 0, then add 1 and keep going like this: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and so on. When you get to 9, you start over with 0 and add another 1, so it's 10, 11, 12, and so on. Peano numbers are named after an Italian mathematician named Giuseppe Peano.