Explore a comprehensive lecture on nonlinear reduced models for parametric and random partial differential equations. Delve into the motivational example, linear reduced models, and performance analysis of reduced models. Examine the model problem, diffusion coefficient, and global error estimate. Learn about the construction of a library, including general ideas and types of partitions. Investigate local error estimates and upper bounds on library size. Study specific sequences with polynomial growth. Analyze numerical examples, including thermal block, multi-cells, state estimation, and single-cell scenarios. Gain insights from Diane Guignard of the University of Ottawa in this 41-minute presentation from the Fields Institute's Workshop on Controlling Error and Efficiency of Numerical Models.