Schematic Diagrams present the internal structure (ports, sub-instances, combinational and sequential logic and connections) :

Flow Diagrams present a high level view of internal connectivity. Multiple connections from one instance to another are collapsed in a single directional edge:

Block Diagrams present the ports:

Finite-State Machine Diagrams present states and transitions by analyzing all the assignments and conditions in which a state variable is used:

All the diagrams can be zoomed and panned.

Click on a block to jump to the chapter where it is documented.