Only three cultures, as far as we know, invented a place value numeration system: the Mayans, the Babylonians, and the Hindu people of India. The current, almost planetary wide, place value numeration system is derived from the Hindu system. It was transmitted to western Europe by the Moslem world.

To help you appreciate that a place value system is more difficult to understand, consider the Mayan numerals shown below. The Mayans compressed at twenty. See if you can figure out how the system works:
Four hundred and twenty-one
One hundred
Two thousand thirteen
A place value numeration system has certain characteristics. Let's examine these characteristics and how they apply to our base 10 (Hindu-Arabic) place value system.
Each place value position is a compression place.

In our base 10 system, ten is the compression point. Thus, the tens place is worth ten ones; the hundreds place is worth ten tens; the thousands place is worth ten hundreds, and so on.
The order in which the digits are written matters.

For example, in our base 10 system, 23 has a different value than 32.

This is not the case in an absolute system. For example, in the Egyptian system, a heel and a staff is worth eleven as is a staff and a heel.
A symbol for zero is used to eliminate confusion about the value for a particular PV position.

In our base 10 system, '0' is the symbol for a count of zero. It allows us to differentiate between 2, 20, 2000, and so on. Note that '0' is not the only place value holder. All digits are place value holders.
The value of a numeral is determined by multiplying each digit by the value of its position and then adding the products.

In our base 10 system, the value of 2905 is determined by:

2 x 1000 + 9 x 100 + 0 x 10 + 5 x 1,

thus, two thousand nine hundred and five ones.
There are as many digits as the value of the compression point.

The Mayan system compressed at twenty; thus there are twenty Mayan digits. In our base ten system, we compress at ten; thus there are ten digits: (0, 1, 2, 3, 4, 5, 6, 7, 8, 9).
The digits roll over whenever '9' is reached. '0' replaces the '9' for the next count up by one (think about a car odometer)
roll over place
roll over place
roll over place
There are two 3 stages lesson plans available on the e-text that directly concern place value. Refer to:
Grade 2 Place Value

Grade 4 Meaning of Decimals