A tree graph is a type of data structure that represents hierarchical relationships among elements. It consists of nodes connected by edges, where each node can have zero or more child nodes, but only one parent node. The top node is called the root, and nodes without children are called leaves. Tree graphs are commonly used in computer science for organizing data, such as in file systems or databases. Tree graphs can also represent various real-world structures, like family trees or organizational charts. They help visualize relationships and make it easier to traverse or search through data. Common algorithms used with tree graphs include depth-first search and breadth-first search.