On the Package Manager window, the indicator lets you know that there are preview packages currently installed in your project. By default, preview packages do not appear in the list of packages you can install; however, you can force the Package Manager to show them by enabling the Enable Preview Packages project setting.
For more information about the verified state and the lifecycle of packages, see Package states and lifecycle.
For a list of stable packages verified for this release, see Verified packages.
Click on any of the following links to see the documentation for the package: