Graphene is an allotrope of carbon with a honeycomb atomic lattice structure. It is a 1 atom thick sheet of carbon atoms arranged in a hexagonal lattice. Graphene constitutes a single layer of graphite.
In an ideal graphene sheet all carbon atoms are bonded with 3 other carbon atoms, giving a sp2 hybridization for each carbon atom.
As mentioned above, graphene has a honeycomb lattice structure which IS NOT a Bravais lattice,and can be described as a Bravais lattice with a basis.
The C-C bond length in graphene is 1.42A.
In the figure above, the 2 red vectors are primitive vectors, while the 2 green vectors are base vectors. There are several different ways of describing this lattice mathematically, but all are equivalent.