We often use numbers like ten, hundred and thousand, and we may also use million or billion, but there are many large numbers which we do not use them regularly. Do you know how many zeros in these big numbers?
When a number is very large, we often use scientific format to write them into power of tens. For example, 1 nonillion has 30 zeros and we write it as 1030.
If we need to list all the zeros, we often use the thousand separator to make them easy to read, for example: 1 billion = 1,000,000,000. Instead of writing as 1000000000, which is very hard to read, we use the thousand separator to have zeros into groups.