Do non residents pay tax in Spain?

Could you please elaborate on the matter of non-residents paying tax in Spain? I'm particularly interested in understanding whether they're liable to pay taxes on their income, assets, or both. Do they have to declare all their worldwide income or just the ones sourced in Spain? Furthermore, does Spain have treaties or agreements with other countries to prevent double taxation for non-residents? Is there a specific tax rate applicable to non-residents or do they pay the same as Spanish residents? Finally, are there any exemptions or deductions that non-residents can benefit from? Thank you for clarifying these points.