Once you have created your package, it's good practice to do further testing (sometimes called regression and/or acceptance testing) internally and/or with a selection of customers. This testing may result in the need to make changes that would normally be blocked if the package version had been installed in production. To give you the ability to do further testing and still make changes, packages are either in Beta or Release state, as described here:

• Release: Release packages can be installed in subscriber production orgs, and can also provide an upgrade path from previous releases. The downside is that you cannot delete the previously released components, or change certain things, such as a field's type. Changes to components that are marked global, such as Apex code methods and Lightning Component attributes, are also restricted. While Salesforce is enhancing the platform to provide the ability to modify certain released aspects, you need to be certain that your application release is stable before selecting this option.
• Beta: Beta packages cannot be installed in subscriber production orgs; you can install them only into other scratch orgs, sandbox, or Partner Portal created orgs. Also, Beta packages cannot be upgraded once installed; this is the reason why Salesforce does not permit their installation in production orgs. The key benefit is in the ability to continue to change new components of the release, to address bugs and features relating to user feedback, after which, you can create another Beta version.

Package versions are, by default, in Beta state. In order to promote them to Release, you need to run the following SFDX CLI command:

sfdx force:package:version:promote 
  --package "FormulaForce [email protected]"