You can see posts that are within a half-mile from where you are. Posts can be viewed through walls and other physical barriers.
If you create a post and want others to see it, just tell someone nearby to download Fabric. They will be able to see your post in the camera-view when you open the app. When they see a number in a small circle (1, 2, 3 etc.) turn toward the number and the post will appear. The number indicates that a post is nearby and way to turn your phone.