For "what" -- I don't specify. Regarding "how I know", I start with several premises:

1) search engines are the dominant way to find information now.

2) conservatively, ≥80% of searches in US are through google.

3) google is not a passive observer of user search queries, but instead actively suggests queries to users.

It follows that there must be some impact. The "engagement" effect is this: I start a search for Depeche Mode, but get distracted by suggestions for J Depp. In contrast, DDG suggests Depakote, Depression, Dept of Revenue and a few other things. Other search engines seem to be less aggressive.