Cellular automata are mathematical models used to simulate complex systems through simple rules. They consist of a grid of cells, each of which can be in a finite number of states, such as "on" or "off." The state of each cell changes based on the states of its neighboring cells, following specific rules that determine how the grid evolves over time. These models can illustrate various phenomena, from the growth patterns of plants to the behavior of traffic systems. One famous example is Conway's Game of Life, which demonstrates how simple initial conditions can lead to intricate and unpredictable patterns.