Every digit in a number has a value that depends on where it sits — we call this “place value.” The units place is on the far right, followed by the tens place, then the hundreds place.
Example: in the number 345, the digit 5 is in the units place, so it's worth just 5. The digit 4 is in the tens place, worth 40 (4 tens). The digit 3 is in the hundreds place, worth 300 (3 hundreds). Altogether: 300 + 40 + 5 = 345.
Understanding place value helps a lot with addition and subtraction, because we learn to add units with units, tens with tens, and hundreds with hundreds — each column on its own.
