You can duplicate an emitter to reproduce the emission elsewhere. For example, you can create an emitter that makes a cloud of particles, then create an identical cloud elsewhere in the scene. You can make the duplicate with or without the original’s connections to dynamic effects such as fields. Expressions applied to the emitted particles are not duplicated.
To duplicate an emitter with connections to dynamic effects
To duplicate an emitter without connections to dynamic effects
Emitters have a hidden Current Time attribute. For an emitter to work when you play an animation, it needs an incoming connection to its Current Time attribute. By default, the input to Current Time is provided by the scene’s predefined time variable. (See Understand the Current Time attribute for details.)
If you select Edit > Duplicate with default options, it doesn’t copy incoming connections to the new object, so its dynamics don’t work. This is why you select Particles > Connect To Time.