You can write numbers in other bases.
Computers usually report their answers in base ten, but they do the computations in base two.
You can think about binary counting in a couple ways. Imagine an odometer with only 1's and 0's, so instead of advancing when the rightmost digit goes from 9 to 0, the second digit from the right advances when the rightmost digit goes from 1 to 0. Or, you can just write down all the decimal numbers that only use 0's and 1's, in order. Exercise Try counting higher. Let's try another example.