Recently, a new interpretation of gravitational spacetime in terms of quantum entanglement has been obtained. The idea of holography in string theory provides a simple geometric computation of entanglement entropy. This generalizes the well-known Bekenstein-Hawking formula of black hole entropy and strongly suggests that a gravitationalspacetime consists of many bits of quantum entanglement. Also a new progress on black hole information problem has been made recently by applying this idea. I will explain these developments in this colloquium.