When you create a post, you can choose to enable "Public Previews" or keep the it obscured. A preview is a great way to get perspective members interested in your content and to drive subscriptions.
When you create a post, you'll see an option to enable or disable "Public Preview."
Here's an example of a post with "Public Preview" enabled -
The content is fully visible
Requires the viewer to join / subscribe to comment
Here's an example of the same post with "Public Preview" disabled -
The content is obscured
Requires the viewer to join / subscribe to comment and access