While chaos is the study of how simple systems can generate complicated behavior, complexity is the study of how complicated systems can generate simple behavior.
Complex systems are spatially and/or temporally extended nonlinear systems characterized by emergent collective properties.

Cellular Automata

(John von Neumann, S. Ulam, and S. Wolfram)

What they are

Game of Life

NxNxN...xN matrix of cell values (that can be real or imaginary values) that change over time according to 1) the status of 'neighbors' (or 'connected' cells, or some external condition) and 2) some rule, which can be global (as here) or local. This 'system' 'evolves' over time.
These system have "attractors"

There are variations in rules, kinds of entities, ...
Vivarium and LifeLab are examples (free or shareware).
Genetic Algorithms
[John Holland - Artificial Intelligence (AI)]

Self-organized complexity (Per Bak)

Sandpile Model
When this occurs it illustrates self-organized criticality.

For a review, perhaps you can look at the Glossary

Comments and suggestions are requested. Please e-mailKeith Clayton