Article writer here! Yeah it's really creepy. In the "Research" tab, youtube tells me what my viewers have been searching for - especially the searches that don't produce many results. Sometimes the search terms are very general (eg: javascript), and sometimes they're more specific (eg: how to [personally identifying task]).

It also shows me what my viewers favourite videos are. Again, the 'highest rated' ones are general. But as you look down the numbers, you can see more specific things.