Now and again I hear older riders talk about gear ratios to each other, like" During a sprint I can handle 93 but not 100."

I Know that these numbers are derived by gears and wheel diameter formula. But it seems confusing to know what is what when everybody uses different teeth numbers on their bike. So I have some questions:

- 1. If it was important to know these gear ratio numbers, and whatever they supposed to mean, why don't most riders (I know) use them?

2. So what is the point of knowing these figures if nobody else knows them (except the older guys)?

3. What is the advantage of knowing these figures?

4. If these ratios are important, how do I get to know these figures?