To VSCode experts - see the screenshot. When right-click on a method with intentions to proceed to the source code:

I am always confused about what to choose: declaration or definition. What is the difference?
InterSystems ObjectScript is a scripting language to operate with data using any data model of InterSystems Data Platform (Objects, Relational, Key-Value, Document, Globals) and to develop business logic for serverside applications on InterSystems Data Platform.