A tree is a nonlinear data structure that models a hierarchical organization. The characteristic features are that each elements may have several successors (called its "children") and every element except one (called the "root") has a unique predecessor (called its "parent"). Trees are common in computer science: computer file systems are trees, the inheritance structure for Java classes is a tree, the runtime system of message indications during the execution of a Java program as a tree, the classification of Java types is a tree, and the actual syntactical definition of the Java programming language itself forms a tree.
Source:
Excerpt from "Data Structures With Java"
by John R. Hubbard, Ph.D.
McGraw Hill
