Facebook page custom audiences allow you to create an audience of people who interacted with your page to be used in ad targeting. This includes both people who do and don’t follow or like your page.
- Everyone who engaged with your page
- Anyone who visited your page
- People who engaged with any post or ad
- People who clicked any call-to-action button
- People who sent a message to your page
- People who saved your page or any post
Some related reading: