I imagine that there was a time when humans did not have different symbols for different numbers. They just made marks in the sand. If they counted five sheep they might have made five marks. If they counted a hundred sheep they made a hundred marks. With very large numbers this marking system becomes impractical. Today we use a base 10 numbering system, in other words we use 10 symbols to represent numbers. Any number can be represented with these 10 symbols: 01234567890. Ten sheep can be represented with only two symbols: 10. The order and placement is very important. 01 does not represent ten, it represents one. Each part of the number is called a digit. The rightmost digit represents ones. The digit to the left of that represents multiples of ten. The digit to the left of that represents hundreds, and thousands, ten thousands, etc. There is no limit to how large the number can be. Each digit represents an amount ten times the amount of the digit to its right. So if someone had 247 sheep, how many sheep would she have? Well you have seven ones, four tens, and two hundreds. So you have two hundred, plus forty, plus seven. Numbers can be represented other ways, too.