After install your lights will function as follows:
Low Beams Only- Only Low Beams will be on
Fog Lights Only- Only Fog Lights will be on
Low Beams & Fogs- Only Low Beams & Fogs will be on
High Beams- Low Beams, Fog Lights, & High Beams will all be on (GM by default normally turns off the fogs when in high beam (& low beams on 03-07 trucks), but this kit solves that)