1) The document discusses vibrations and waves, defining key terms like amplitude, period, frequency, and phase. It describes the motion of a pendulum and how its frequency is related to its length. 2) Resonance is defined as occurring when energy is added to a vibrating system at the same frequency and phase as the natural frequency, potentially causing a continuous increase in the system's energy over time. 3) Examples of periodic and simple harmonic motion include a pendulum and mass attached to a spring. The document provides links to videos demonstrating resonance and vibration concepts.