Have a 2005 Buick LaCrosse... Can anyone tell me what "cat protection" does/means?

Probably something to do with the cat converter. Have you checked for codes?

Under what conditions did the condition present itself?

It'* either a feline wellness aid, or detecting/preventing a catalyst damaging condition (severe misfire) is my guess. Given the typical target demographic of Buick, it'* a 50/50 shot either way

Under what circumstances is this term used? I mean, where did you get or hear the term?