Graphene is a new 2D nanomaterial with outstanding material, physical, chemical, and electrochemical properties. In this review, we first discuss the methods of preparing graphene sheets and their chemistry. The fundamental reasons governing the electrochemistry of graphene are then described. Graphene is an excellent electrode material with the advantages of conductivity and electrochemistry of sp2 carbon but without the disadvantages related to carbon nanotubes, such as residual metallic impurities. We highlight important applications of graphene and graphene nanoplatelets for sensing, biosensing, and energy storage.