Place value in mathematics is the value represented by a digit.
In the decimal system (which is base 10) with digits (0-9) the first column left of the decimal place is the units column, the next column to the left is the tens, the next is the hundreds. The first column right of the decimal place is the tenths column, the next is hundredths, the next is thousandths.
This can be illustrated as H T U . t h th