Is there a difference between a package and a plugin?
  Yes, there is! Both are packages,
  but a plugin is a type of package that contains 
  platform-specific code (such as Kotlin, Java, Swift, Objective C)
  that communicates with the underlying platform.
  For more information, see Using packages.

Some features of WorkManager include:

Persistent work handling

Flexible scheduling

Ability to apply constraints on jobs like checking for a network connection, 
only running when the device is charging, or only running when a device is 
idle (Android only)

Useful links

Android setup

iOS setup

Dart concurrency

Geolocation