A Lindenmayer System is a formal grammar that was initially conceived as a theory of plant growth. L-Systems can generate complex forms with relatively few simple rules.

L-Systems consist of two parts: a generative and an interpretative process. The main concept of the generative process is string rewriting, in which the letters that comprise an initial string are replaced by other letters according to pre-defined rules. The replaced letters form a new generation of string which is then subject to the established replacement rules. This string rewriting process is usually repeated for several generations.

In the second part of the L-System, the letters of one or multiple generations of string are interpreted and visualized. For instance, letters of a string can be visualized by mapping them to attributes of objects or alternatively by interpreting them as turtle graphic commands.