Gen's right, 'g' is for actions and 'y' is for tools. If you open up the option box for many of the actions and tools, you can see in the Edit menu that you can actually use many of them "as action" or "as tool". I think the main difference is that tools are typically active until you select another tool or manipulator like rotate or translate, whereas an action is executed and that's the end of it.

(Of course now that I say that, I can see exceptions in maya, but I'm hoping that's the general behaviour)