Graphene is a two-dimensional honeycomb lattice of carbon atoms and it has recently attracted considerable attention because of its peculiar electronic structure in which the extra sublattice/layer degrees of freedom, called pseudospin, play an important role. In this talk, using standard methods such as tight-binding model, Boltzmann transport theory and mean-field approximation which appear in undergraduate level text books, I discuss electronic structure, optical and transport properties, and interaction-induced ordered states in graphene systems. Next, I describe the prospects for a new type of electronic device scheme, called pseudospintronics, in which the operation is based on collective electronic behavior.