So in plot development, there are a few elements established early in the story themes, actions, situations, contrasts, whatever that have some sort of fictional potential energy, i.e. the reader/viewer will want to see what becomes of them.
A plot is a causal sequence of events, the "why" for the things that happen in the story. The plot draws the reader into the character's lives and helps the reader understand the choices that the characters make.
Example, in a mystery, the author will withhold plot exposition until later in the story.
