I will describe general facts about entanglement entropy in QFT and discuss two different ways to get rid of the regularization ambiguities, using mutual information and relative entropy. Then i will show relative entropy gives a proof of a well defined version of the Bekenstein bound, an offer a strong test to holographic entropy. It can also be used to do "vacuum state tomography" from the entropy functional. In a second part of my talk I will show mutual information can be used to give a precise unambiguos definition of the central charge in the c-theorem for d=3, which in principle can be computed using any regularization. I will revise the proof of the c-theorem in terms of mutual information.