A two-digit number like 23 is composed of 2 tens and 3 ones (meaning 20 + 3). Understanding place value reveals that the position of a digit determines its value—fundamental to all multi-digit arithmetic.
Use base-ten blocks, bundle sticks, and place value charts. Have students represent the same number in multiple ways.
Think about counting a large pile of sticks. If you count them one by one, it is easy to lose track. A better strategy is to bundle every 10 sticks together with a rubber band. Then you count the bundles and the leftovers separately. A number like 23 is telling you exactly this: 2 bundles of ten (that is 20 sticks) plus 3 loose ones (3 more sticks). Together, 20 + 3 = 23.
The critical idea is that where a digit sits determines what it means. In the number 23, the digit 2 is in the tens place — it means two tens, or twenty. The digit 3 is in the ones place — it means just three. Now look at 32: the digits are flipped, but the values are completely different. The 3 is now in the tens place (thirty), and the 2 is in the ones place (just two). Same digits, very different numbers.
This is why skip-counting by 10s is the right prerequisite. When you practiced "10, 20, 30, 40 …" you were already building groups of ten in your mind. Place value just names that idea and gives it a visual form: in any two-digit number, the left digit counts the tens-groups, and the right digit counts the leftover ones.
You can make this concrete with base-ten blocks. The long rods each represent a group of ten; the small cubes each represent one. Build 47 using 4 rods and 7 cubes, then build 74 using 7 rods and 4 cubes. Seeing how different those two piles look makes the meaning of digit position impossible to forget.