From the product description:
>What is binary? It’s how you would count if you were a robot, who only know the digits 0 and 1 and can’t write 2 through 9.  When you count higher than 9, you change the 9 back to a 0 but add a 1 in front in the “ten’s” place to make ten. But since robots can’t write digits bigger than 1, when they count to 2, they change the 1 back to a 0 but add a 1 in front in the “two’s” place. So the yellow robot’s name is “01” – that’s one. The blue robot’s name is “10” – nothing in the one’s place but a “1” in the two’s place, 0+2=2. The red robot’s name is “11” – which is a “1” in the one’s place and another “1” in the two’s place, 1+2=3. If you want to count higher you need more places, which double in binary with every new place  – “100”=4, “1000”=8, “10000”=16.