Essential
The Essential field defines whether a package is viewed as being essential. This prevents you from remove it once installed, at least not without using the --force-remove-essential command line option.
The default value of the Essential flag is No meaning that the package can be removed without the --force-remove-essential command line option. This means if the package is Essential, the field is required (must be specified.)
Example:
Essential: Yes
The field is a flag and it only accepts Yes or No as a valid value. The package checks and if the field is set to anything else an error is generated.
The wpkg package is marked as essential since removing it would prevent you from managing your installation!
