In Wayne McDill's book, 12 Essential Skills for Great Preaching, he says that sermon development takes on four forms, each with its particular contribution to the support of sermon ideas. These include Explanation, Illustration, Argumentation, and Application. McDill argues that when the sermon material is out of balance, what you say does not have the clarity and impact you hope for.
I've posted two articles which are excerpts from his book. The first shows what happens when each of the elements is too dominant or too weak. In the follow up article, McDill uses a chart to explain how to balance them.
Read about Four Critical Elements of Preaching in LifeWay's Proclaim Online and find a link to the follow up article.