This article describes the fundamental phenomena of cavitation. The distinctive characteristics of cavitation in the marine applications, especially in the propellers, are introduced. This article explains first the quasi-steady processes in phase transitions of pure substances. Next, the bubble dynamics are explained as well as the Rayleigh-Plesset equation that is used to describe the single bubble dynamics in a liquid medium. The bubble stability and its effect on cavitation inception are also discussed. The noise and erosion that may be induced by cavitation bubble or cavitating cloud collapse are shortly introduced. The common cavitation types on marine propellers and the conditions in which they occur are described. The cavitation types are demonstrated by photographs of cavitating model propellers. Finally, the dynamics of sheet and tip vortex cavitation are explained in more detail. The inception conditions and the shedding mechanisms of sheet cavitation are explained. The potential flow vortex model is introduced as well as the viscous effects in the vortex core. The disturbances in the vaporous vortex core are discussed shortly.