If you have a popular YouTube channels with more than 5,000 subscribers, you'll be able to find more about the people who love your videos. "The Fans page shows a list of some of your most engaged and most influential fans, based on their public interaction with your YouTube channel. By default, the list is sorted by a combination of subscriber count and engagement level, but you can also sort by either factor on its own," informs YouTube.
"For each person on the list, you can see how many subscribers they have, how engaged they are with your channel, an example comment they've left on one of your videos, and how long they've been a subscriber. Engagement is based on that person's public interactions with your channel, such as commenting, liking, subscribing, etc."
You can also create a Google+ circle for your top fans in the insights page. "See what other videos and channels they're into, and reach out via Google+ to ask a question, start a conversation, share behind-the-scenes photos, or upload a private video just for them."
{ Thanks, Stefan. }