This chapter introduces the vibrations in a simple manner. The basic concepts of degrees of freedom and of discrete and continuous systems are introduced, along with a description of the elementary parts of vibrating systems. The various classifications of vibration namely, free and forced vibration, undamped and damped vibration, linear and nonlinear vibration, and deterministic and random vibration are indicated. The various steps involved in vibration analysis of an engineering system are outlined, and essential definitions and concepts of vibration are introduced. The concept of harmonic motion and its representation using vectors and complex numbers is described. The basic definitions and terminology related to harmonic motion, such as cycle, amplitude, period, frequency, phase angle, and natural frequency, are given. Finally, the vibration analysis procedure is introduced with some examples.