eli5: Every base is base 10

Question

Something I found while reading about base systems, I can’t really wrap my head around it. Maybe it has to do with fractions?

In: 41

Answer 1

The joke is, how do you write “2” in base 2? You write it 10. (One two and no ones.) Thus, it is base “10.”

How do you write “3” in base 3? You write it 10. (One three and no ones.) Thus it is base “10.”

Etc.