What Google Analytics data can be used to define a remarketing audience?

To define a remarketing audience in Google Analytics, data from a pre-defined segment is highly relevant. Pre-defined segments in Google Analytics allow you to group users based on specific criteria, such as their behavior on your site, traffic source, or other characteristics. This categorization enables you to create audiences that can be targeted with remarketing campaigns, which are designed to reach users who have previously interacted with your website. Essentially, pre-defined segments provide a convenient way to leverage existing user data to identify and target specific groups efficiently.

Custom segments can also be utilized, but since the question focuses on the type of data that can be specifically used for defining remarketing audiences, pre-defined segments hold a more direct application in this context. Custom dimensions and custom metrics serve more analytical purposes, helping track specific attributes or behaviors of users, but they do not directly correlate to the creation of remarketing audiences.