What is a Global Switch Hook?

After installing this image editing software (Photoscape PhotoScape : Free Photo Editing Software (Photo Editor) Download ), CFP notified me that Photoscape wanted to add a global switch hook to Firefox. Being unfamiliar with Photoscape and not knowing what a global switch hook was, I denied it. As far as I can tell the program was not compromised.

So, is a global switch hook: Recommended? Safe? Required?

PS A site-search produced a few hits, but nothing useful.