Liquid interfaces are ubiquitous and of fundamental importance in many physicochemical phenomena, such as atmospheric reactions on aerosol particles, cavitation bubbles, biochemical reactions, and so forth. The interfacial region is very limited in space and has unique properties compared to the bulk due to its heterogeneous environment. Molecular simulation is a powerful technique to elucidate and predict physical and chemical properties of interfaces with thickness of nm order. In this review, we focus on the recent progress of the simulation studies of molecular structure, vibrational spectroscopy, and transport phenomena at the interfacial region. A key experimental technique to elucidate interfacial molecular structure is the interface-selective vibrational sum frequency generation (VSFG) spectroscopy. A close collaboration of VSFG studies with molecular simulation has opened an avenue for understanding new aspects of the structures of aqueous surfaces. We discuss some important properties of water to interpret the interfacial vibrational spectra. We further review the recent development of the simulation studies for the transport phenomena associated with condensation and evaporation at liquid interfaces.