You can reach new audiences by broadening your ad group's targeting criteria or using a Lookalike Audience. There is behavior targeting and interest targeting.
Behavior targeting is based on actions recently taken in the past 7 or 15 days. There are two behavior categories that focus on user's recent interactions with content:
Video-related Actions: Behavior includes users' engagement (video completion, like, comment, share) with organic video content in the past 7 or 15 days.
Create Following Actions: With two types of engagements:
Following: Targets users that follow specific type(s) of creators.
Viewed Homepage: Targets users who have viewed profile pages of specific type(s) of creators in the last 30 days.
Interest targeting is a prediction based on actions and other factors occurring over a longer time period.