Definition: The relationship between an original statement and one clarifying its meaning. The clarifying proposition may expound on only one word of the associated arc or its entirety.
Conjunctions: that is, etc.
Distinctions: Action-Manner, Comparison, Ground (Hover over a relationship to see how it differs.)
Action-Manner (Ac/Mn) vs Idea-Explanation (Id/Exp)
Action-Manner can be thought of as the Idea-Explanation of verbs.
Whereas with Idea-Explanation we find the explanation describing a single noun or an entire concept, Action-Manner tells us more about the action happening. You should be able to paraphrase an Action-Manner with the word "by."
Bill drove to New Jersey, speeding the entire way. (Action-Manner)
Bill drove to New Jersey, going home to where he grew up. (Idea-Explanation)
Comparison (Cf) vs Idea-Explanation (Id/Exp)
Comparison is more specific than Idea-Explanation. Thus, when you find a proposition that is explaining another more through the use of comparison, it is better to use the Comparison label as the "deeper" relationship.
That restaurant serves amazing pizza, like the kind they make in Italy. (Comparison)
That restaurant serves amazing pizza; its deep dish crust is second to none. (Idea-Explanation)
Idea-Explanation (Id/Exp) vs Ground (G)
"For" or "because" are common connecting words which indicate a Ground relationship. However, sometimes, we find these words presenting more of a further explanation of what preceded, not a different idea which grounds what came before.
The easiest way of determining which relationship is more appropriate for a given text is to ask whether the author/speaker is restating what was said before with further explanation (Idea-Explanation) or making a distinct statement which supports what preceded (Ground).
Jesus is glorious, for he shines forth perfection. (Idea-Explanation)
Jesus is glorious, for he is just like the Father. (Ground)