Learn about Parton Distribution Function (PDF) uncertainties and validation methods in this comprehensive two-part lecture from the Galileo Galilei Institute. Explore the fundamental concepts, methodologies, and statistical frameworks used to assess and validate PDF uncertainties in particle physics. Gain insights into the technical aspects of PDF error estimation, validation techniques, and their practical applications in high-energy physics research. Delve into both theoretical foundations and practical implementations while understanding how these uncertainties impact physics analyses and experimental results.