This lecture covers the basics of laser operation, including light-atom interaction, gain, resonators, and noise characteristics. It also delves into different types of laser systems, such as gas, solid-state, and semiconductor lasers, as well as ultrafast lasers and nonlinear frequency conversion. The presentation includes theoretical models like the electron oscillator model and absorption coefficients, along with practical demonstrations in the laboratory. The discussion extends to refractive index, dispersion, and the quantum vs. classical views of the atom, emphasizing the Lorentz model and stimulated emission. The lecture concludes with topics like absorption cross-section, spontaneous emission, and Doppler broadening of spectral lines.