Either pay-per-click banners or offers to install another software in bundle (the latter being way more common).
For example when installing Java, you see this "offer":
![[IMG]](proxy/V%2FlNRoM4xHTn%2BvRHoNpIxLtxJVrKZmrH8TsgEnwSANWYCICbeJ7paexzogQZgVddxaqB7HNyiWZPFg1LJT%2FYxtufvjypd59QohimTDs1RRTuygjtSTL6TpH0W62b8li%2FLOiJi9boGpfy1UhhrA8BeEilPDHGlbCfk2G4gSbIzz85tF1yKOYk2fGBt2lGVdozJps%3D/image.png)
I think that Ask Toolbar option is some kind of affiliate/CPI advertising,...
Monetizing software installer
from Pay Per Click Advertising http://ift.tt/1VqkRua
via IFTTT
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