Galois groups and groups of Dirichlet characters

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Assume we have Galois extension $K/\mathbb Q.$ Let be $(G,\circ)=\text{Gal}(K/\mathbb Q)$ its Galois group and let be $(X,+)$ group of Dirichlet characters, that "belongs to this field extension". Now, what is relation between $X$ and $G$?