Customer List audiences are created by:

Customer List audiences are a type of custom audience on Reddit (and other platforms) that allow advertisers to target specific users based on information they already possess. This is achieved by uploading a CSV file containing identifiers like email addresses or mobile ad IDs. Reddit then matches these identifiers to its user base, creating a targetable audience. Identifying top users in related subreddits describes interest-based targeting or community targeting, not a Customer List. Modeling people similar to people who have converted on other campaigns describes a lookalike audience, which uses an existing audience as a seed to find new, similar users. Finding people who have engaged with your ads on Reddit describes retargeting, which focuses on users who have previously interacted with your brand.