What does approving and ignoring domains do?

"Approve" and "Ignore" are functions designed to help you quickly mark image matches or domains that are either legitimate uses of your work (are under license, or otherwise acceptably used) or to hide a non-actionable match or domain from your matches (i.e. non-commercial use, no contact information, etc.).

You can manage both ignored and approved matches on your profile settings page.

Match Actions - overview

By approving or ignoring domains, it will help you in the future to avoid seeing matches that are on websites you do not wish to pursue or are not viable for case submission.