In this talk we will first review the Shannon and Renyi entropies as information theoretic concepts and their use in quantum and classical systems. They are quantities which usually base dependent. Then we will introduce mutual Shannon and mutual Renyi entropies as very useful quantities to detect the universality classes of the quantum spin chains. We will present some conjectures regarding the connection of these quantities to central charge of the critical systems and then we will support them with numerical works done on the Ising model Q=3,4 Potts model and XXZ spin chains. In all of these cases we will emphasize on the bases that one chooses to calculate these quantities and in particular we will show that some of the bases are actually more suitable to detect the universality classes. References: 1: FC Alcaraz, MA Rajabpour, Phys. Rev. Lett. 111, 017201 (2013) 2: FC Alcaraz, MA Rajabpour, in preparation.