This document provides an overview of pulmonary function tests, with a focus on spirometry. It discusses the anatomy of the lungs and airways. Various lung volumes and capacities are defined, including tidal volume, inspiratory reserve volume, and total lung capacity. Spirometry is described as a test that measures airflow into and out of the lungs. Forced vital capacity, FEV1, and FEF25-75 are key spirometric measurements. The document reviews obstructive, restrictive, and mixed lung disease patterns based on spirometry results. Clinical applications and case examples are also briefly mentioned.