A digit's position and the value it represents in a number it is what?

To answer your question let's look at one example, the number 345. The 3 tells us there are 3 hundreds. It is in the position that is 3rd from the right. The 4 tells us there are 4 tens and it is the digit 2 from the right, and the 5 tells us there are 5 ones and it is the right most or ones digit. The ways to think of this, in our usual base 10, is that each digit's position is a power of 10. The ones are 10^0 since 10^=1. The next digit is 10's and we view it as 10^1. Then the hundreds since the third position is 10^2. So we have 5x10^0+ 4x10^2+3x10^3, Some might say why bother with all this? There are many answers, but one reason is that thinking of the numbers and digits this way lets us easily change to any other base, such as base 2 or 8. In the case of base 2 the right most digit is 2^0 or 1, the next is 2^1 or 2's, then 2^2 or 4s etc.