This is how "deep" a character is. It involves questions like why the character does what the character does, what the character thinks, feels, desires, and hates, where the character came from, and/or how the character sees the world. It may be there in Subtext, but it still affects the depth of the character. This is often known as a character being One-Dimensional, Two-Dimensional, or Three-Dimensional. The Three Dimensions can be thought of thus: Breadth: Variation within a character. The amount of different traits that define them and how well these interact.