I've been reading the book Godel Escher Bach: an eternal golden braid and while I can understand most of the concepts in the book some of the math is a little fuzzy.

The author presents as an example an infinite tree diagram "diagram G". In two of the four nodes of the diagram he writes the letter G to stand for a copy of diagram G. In this way the diagram can be expanded indefinetly. I'll post an image if I can figure out how.

The formula is:
G(n)=n-G(G(n-1) for n>0
G(0)=0

The paragraph below this starts

"How does this function G(n) code for the tree structure? Quite simply, if you construct a tree by placing G(n) below n, for all values n, you will recreate diagram G."

What does he mean by placing G(n) below n? And what is the difference between G(n) and n, aren't they the same value?