1, digits: refers to the position occupied by each digit in a number. For example, from the right, the number of digits in the integer part is the unit, ten, hundred, ten thousand, one hundred thousand, one million, ten million, one billion, ten billion and one hundred billion.

2. Number of digits: refers to the number of digits of natural numbers. A number containing a number is a number, such as the natural number 9, which is just a number, so it is a number; Numbers containing two digits are two digits, such as natural number 99, which contains two digits, one and ten, so it is two digits; Numbers containing three digits are three digits, such as natural number 999, which contains three digits, ten digits and hundred digits, so it is three digits.