What is the purpose of these commands?:
1 Answer
As far as I know, this feature is only available if it's supported by the language you're using. For example, it's available with several bundled languages such as PHP or JavaScript.
When your cursor is over a function declaration (or when it's selected), you can use Goto Reference to jump to all calls of that function within your project. Using Goto Definition works the other way round, hover over a function call let's you jump to its definition.
Personally, I prefer using Sublime Text's tooltips that display definitions and references when hovering a function call.
Example:
