Practically, what does HFT actually mean to ad business? Am I correct that it's about being able to bid for ad placements according to real-time CTR/CPA analyti

Practically, what does HFT actually mean to ad business? Am I correct that it's about being able to bid for ad placements according to real-time CTR/CPA analytics? That would be neat, I can imagine writing automated robots distributing your ads in sub-optimal ways, moving with your target audience from website to website during the day.