An appositive is a noun that adds a second image to a preceding noun. The appositive expands details in the reader's imagination. For example, by adding a second image to the noun raccoon in the sentence “The raccoon enjoys eating turtle eggs,” the writer/artist can enhance the first image with a new perspective.
For example, the writer might paint the sentence **“The raccoon, a scavenger, enjoys eating turtle eggs.” Scavenger follows raccoon in the sentence; it's set off with commas and enriches the image of the painting.