"Kateřina is buying a new suit for her husband."
Translation:Kateřina kupuje pro svého manžela nový oblek.
It is condidered germanism and not standard Czech, but you would be understood.
"Svůj" means "one's own / belonging to the subject / of the subject / related to the subject". It is reflexive possessive pronoun, thus rendered as possessive pronouns including my, your, his, her, our, their, depending on the subject.
Vidím svého otce. — I see my father.
Kateřina se loučí se svými sestrami. — Kateřina says goodbye to her sisters.
Matky obvykle milují své děti. — Mothers usually love their children.