Move the slider for each place and watch how the size and number of blocks change, and how the number is read out loud.
The number 222 has the digit 2 written three times, but each one stands for a different size. The first 2 means 200, the middle 2 means 20, and the last 2 just means 2. The same digit means something completely different depending on which place it's in — that's called place value.
In the place-value blocks, the ones place is shown as a single small cube, the tens place as a rod made of 10 of those cubes stuck together, and the hundreds place as a flat made of 10 rods stuck together. Watching the block get exactly 10 times bigger each time you move up a place makes it really click why place value grows by a factor of 10.
Move the slider for each place and see how the blocks' size and count, and how the number is read aloud, change together.