Once a coach has broken each route down into these three sections, he can start to see the different stages, and objectives of each segment within each route.
Running routes is one of the most under-coached aspects of football. The same way an offensive lineman needs to be coached on the details of each of his steps, wide receivers need to be taught the finer points of the routes they are running. We break our route running down into segments. We tell our receivers that each route has three basic parts to it that must be mastered.
Part 1: The first part of any route is the stem. This is the first 3 steps of the route. The objective of the stem is for the receiver to gain a leverage advantage on the defender. This could mean a lot of different things depending on the route and the coverage that he is facing, but if a receiver is not able to successful gain a leverage advantage over the defender, he is going to be put in a position of disadvantage that he will struggle to overcome over the course of the route.