Please explain Save vs. Spells Items (realistic)

[grandmaster_foo]

aka items with name 'Realistic'

I hate items like this, it is unclear what it helps to resist. Is this any spell cast upon you? Is it specific spells that are subject to spell resistance? Is the value added to all your spell save attempts even if the spell is resisted say using Will, Fort, etc?

Thanks!

edit: Just tested this. The item gives a non-stacking enhancement bonus too will, fort and reflex. This is greatly confusing to other items that specifically call this out with "Resistance", making one believe they can gain additional saves.