Not sure how I can create a pyramid diagram with a centerline down the middle to the upper-most point for display, so I'll just word it out again.
A pyramid with a center-line straight down the middle to its upper-most point can be used to describe the optimal situation from which best plays/moves are considered while playing a game of Go. "Fringe" moves/variations, are moves that are on the outlying edges of the pyramid or in general are moves that exist outside of the centerline in the pyramid structure we are describing.
Therefore, using this structure we can deduce that the centerline up the pyramid is the most efficient and optimal way to get to the top of the pyramid. There may exist an optimal structure for playing moves in Go that reflect this structure and when considering moves in Go you should always make core plays that involve backup plans or just solid moves in general that work. This pyramid structure for best moves is useful in helping us visualize what fringe plays are and how to avoid them so we can understand that there exists optimal moves in the game of Go that get us to where we want to go faster than if we were making fringe plays.
This is similar to the center theory of play found in chess opening guidelines. Although it differs a bit because in Go, one may not necessarily open the game with plays in the center but rather in thecorners for optimal play.
Keep in mind, however, that fringe plays can also get us to the top of the pyramid (by crawling along the edges, similar to crawling along the edges of a board to make territory which results in inefficient territory), but they may not be the most optimal branch of play.