It's an ignition noise capacitor. It helps stop ignition noise from interfering with the radio or sensitive computer circuits like the crank sensor or wheel speed sensors.
Ah, ok. Wix 51515 as well (NAPA Gold 1515), interchangeable with FL1A. By the way, does anyone know where the FL1A is made? Being a Purolator-manufactured filter, is it made in NC at one of the Purolator plants (Shelby maybe)? Interesting choice, as both brands (Wix and the FL1A Purolator) are both potentially made locally (in-state). They also have the same parent company now too, as Mann+Hummel owns both.
They're both about $4 on Rock Auto; they're both regarded as great filters and I'd use either one. I've only used the Wix.