When you create an audience, it is automatically exported to any of the accounts you have linked to Analytics (e.g., your Google Ads account), and you can use the audience in those accounts as the basis for remarketing.
For example, you might want to remarket to users whose behavioral history includes the first_open event, but not the in_app_purchase event, or includes the add_to_cart event but not the purchase event.
Learn more about creating audiences, and about using include and exclude conditions.
Keep in mind that iOS-app users who opt out of having their activity tracked (via the ATT prompt) will not be included in audiences that are exported to Google Ads.