A "Child Node" refers to a node in a data structure, such as a tree, that is directly connected to another node, known as the parent node. In this context, the child node can hold data or point to other nodes, forming a hierarchical relationship. This structure is commonly used in computer science for organizing data efficiently. In a tree structure, each parent node can have multiple child nodes, but each child node has only one parent. This relationship helps in various applications, including file systems, XML documents, and database management, where data needs to be organized in a clear and accessible manner.