Explore the intricacies of entanglement in quantum field theory and quantum gravity in this comprehensive lecture from the Kavli Asian Winter School on Strings, Particles and Cosmology. Delve into the Page Curve paradox, unitary theory, and the concept of islands in quantum information. Gain insights into reconstructing the interior of black holes and understand the significance of replica wormholes in quantum gravity. Examine key equations and their implications, and participate in Q&A sessions to deepen your understanding of these advanced topics in theoretical physics.