When should you use custom audiences?
Have you ever searched for something using a “keyword”? When you did that, you were likely provided a long list of searches that involve that keyword in one way or another. This is one way that advertisers create custom audiences that include other users with similar interests as you. There are a variety of factors that advertisers should consider when creating custom audiences based on affinity. I think demographics, knowledge of the audience’s interests, and display are the most important factors. How could you create a custom audience without really knowing who your audience is?
Here are some important factors to consider:
As an advertiser, it is important to know the details of the audience you’re working with. It is helpful to know their age, ethnicity, gender identity, culture (etc.) to adapt targeted ads to their preferences. Many companies also use cookies to track user’s search history to provide ads for products that they want. Knowing the specific interests of your audience helps to create a detailed idea of products they would likely be interested in buying. Display is a campaign type for custom audiences that focuses on the user’s passions, interests, habits, and recent purchase intent (“About Audience Targeting”). The appearance of an ad has to fit the preferences of the targeted audience. There are many factors to consider when creating a custom affinity audience, but I believe these are the most important.
https://support.google.com/google-ads/answer/2497941?hl=en&ref_topic=3122880