Galois representations viewed as the fundamental group of $2,3,5,... \infty$

Question

In a paper of T. Saito

http://www.ms.u-tokyo.ac.jp/~t-saito/pp/GR2.pdf

he said that the Galois group $\text{Gal}(\mathbb{Q})$ could be seen as the fundamental group of the set $2,3,5,... \infty$. The local systems over $2,3,5,... \infty$ could be seen as determined by the representations of $\text{Gal}(\mathbb{Q})$. I don't really understand why, could anyone elaborate on this analogy?