How to get a Reference to the Element that Triggered an Action

I am trying to build a new plugin for a new Action.

From inside the action code, How would I get a reference to the Element that the action was attached to?

Also, the explanation for context.keys says it’s an object with keys defined in the Plugins Tab? What exactly does this mean?

Is there a way to get the Element drop down/search box, the same way for the built in actions like Show/Animate?