It's a database full of users that can be used for connecting with subject matter experts if you want to ask questions or ask for feedback/improvement on an application, or for research on anything

this can save you a ton of time on finding experts to ask questions to (like you said, it is used for reaching out directly)

And I am still experimenting for the best scraping algorithm to get the best experts, as I check various factors to filter out the best users in each subreddit