A Page Graph is built from a combination of two scripting languages.
See Step-By-Step Page Graph for the table of contents.
---- The second graph on Page Graph HERE Node was created with this markup (leaving aside the beginning boilerplate).
node [style=filled fillcolor=lightyellow penwidth=3 color=black fontname="Helvetica"] HERE NODE node [fillcolor=white] LINKS HERE -> NODE
That's a combination of the DOT 
graph-description language and Fedwiki-specific commands. DOT commands are in lower case, Fedwiki commands in upper case. The whole thing is often referred to as "the markup."
When a page containing a page graph factory is loaded or reloaded, all the markup is processed and turned into pure DOT commands . To see such commands, Toggle Editing Mode, double-click on the following graph, and scroll down past some strategically-placed whitespace.
DOT strict digraph rankdir=LR node [style=filled fillcolor=lightyellow penwidth=3 color=black fontname="Helvetica"] HERE NODE node [fillcolor=white] LINKS HERE -> NODE STATIC strict digraph {rankdir=LR node [style=filled fillcolor=lightyellow penwidth=3 color=black fontname="Helvetica"] "Page Graph Links From HERE" node [fillcolor=white] "Page Graph Links From HERE" -> "Step-By-Step Page Graph" "Page Graph Links From HERE" -> "Page Graph" "Page Graph Links From HERE" -> "Internal Links" "Page Graph Links From HERE" -> "Page Graph HERE Node" "Page Graph Links From HERE" -> "Internal Links" "Page Graph Links From HERE" -> "How Page Graphs Work" }
You should see this:
STATIC strict digraph {rankdir=LR node [style=filled fillcolor=lightyellow penwidth=3 color=black fontname="Helvetica"] "How Page Graphs Work" node [fillcolor=white] "How Page Graphs Work" -> "Page Graph" "How Page Graphs Work" -> "Page Graph HERE Node" "How Page Graphs Work" -> "Toggle Editing Mode" }
Those DOT commands are sent to a DOT processor, which produces the pretty picture.
Note: if you copy the whole content of a page graph factory, including the `STATIC` part, then paste it into a new page graph somewhere else, it does no harm. The `STATIC` part will be overwritten before the graph is shown.
Next: Page Graph Links TO Here