Lattice models are mathematical frameworks used to represent complex systems in a simplified manner. They consist of a grid or lattice structure where each point, or node, can represent a variable or state of the system. These models are commonly used in fields like physics, materials science, and statistical mechanics to study phenomena such as phase transitions and critical behavior. In lattice models, interactions between neighboring nodes can be defined, allowing researchers to simulate and analyze how changes in one part of the system affect the whole. Examples include the Ising model for magnetism and Percolation theory for understanding connectivity in networks.