Decimal numeration system
There are many number systems. The base of a system determines the place value of each digit. The number system where place values are powers of 10 is called the decimal numeration system. The digits used in this system are 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. When no base is given, base 10 is assumed.

The exponent the base is raised to increases by one with each movement to the left. The decimal place value of the digit immediately to the left of the decimal point is 1, or 100.
The place value for the digit immediately to the left of 100 is 10, or 101.
The place value for the digit immediately to the left of 101 is 100, or 102.
And so on.

The number 10,342 means that there are:
two 1's (or 100)
four 10's (or 101)
three 100's (or 102)
zero 1000's (or 103)
one 10,000's (or 104)
Therefore, 10,342, in the decimal system, is equal to 21 + 410 + 3100 + 01000 + 110,000 in expanded form.