During the initial stage, this feature was only available for beta testers, but YouTube is slowly making it available to more and more creators. 

Community is available in the main channel page and the goal is to continue to expand the concept of community on YouTube, helping you to be closer to your audience. What's great about this is that you can be creative on how you use it, as there are many ways to interact with your audience, such as:

• Getting involved with your community: Ask your fans what to do next in your channel. They appreciate the fact that their opinion matters, and you may get some great ideas. You can even create polls.
• Bringing fans backstage: Post an image (can be an animated GIF) that shows what's coming next to your channel. This is interesting because it can help you fill the blank spaces in between your video posts, especially if your video productions take time to complete. 
• Increasing your reach: You can easily cross-promote and share another channel's video that you think your audience may be interested in.
• Improving discoverability: YouTube also has ways to promote your Community posts to the right users in your audience, and your most engaged viewers can now see Community posts in their Home feed, even if they haven't subscribed to your channel. The notifications have been optimized so that your fans are eligible to receive them, but they won’t necessarily get a new notification for every new Community post.

To learn more about community posts, click here. You can also learn how to take advantage of this feature to interact with your audience by going here.