The goal and the end result of the audience and page search is the same i.e. to provide you with related interests for your Facebook Ads targeting. However, main difference is how we find those interests.
On the Audience Search page, we directly search through in the database of interests that can be targeted using Facebook Ads.
Here's a video about the audience search:
On the Page Search page, it works slightly different. On this page we initially search for Facebook Pages. However, not every Facebook Page can be targeted using Facebook Ads, which is why we automatically check every result to see if there is a matching Facebook interest.
Here's a video about the page search:
Our advice is to use both ways of searching, so you’re able to find more interests to target.