Linked graphite is an allotropes (elements that exist in two or...

Linked graphite is an allotropes (elements that exist in two or more different physical forms) of carbon so as diamond which is the most complex interms of is structural bonding. Unlike diamond each carbon atom in graphite is conjoined by convalent bonding to 3 other C atoms. When you stack all these bonds up it forms graphite in a trigonometrical fashion. Graphene is only one "planar" or sheeted carbon, simply, it is the simplest form of C.
Say, if you combine 10 sheets of graphene you arrived at graphite and if you combine 100 graphene sheets you get diamond.