18 minutes ago, mcstroom said:

It's illustrating what can be made from what.

A common game to test organic chemistry knowledge is to ask the student to show a route for synthesising a given compound, using only alkanes or something very simple as the starting point. We got very good at that in my first year at university. I still have a copy of R O C Norman's "Principles of Organic Synthesis" on my shelf. One learns a "vocabulary" of synthetic reactions, which can then be deployed to construct a wide range of molecules. 

This scheme shows you a range of steps that interconvert various types of organic functionality.