A binary tree is a type of data structure composed of nodes, where each node has at most two children, referred to as the left child and the right child. It is called a "binary" tree because it represents a hierarchy where each node can have a maximum of two children.
In a binary tree, the topmost node is called the root. Each node in the tree can have a left child, a right child, or both. Nodes without any children are called leaf nodes or terminal nodes. All other nodes are called internal nodes.
The binary tree structure allows for efficient searching, insertion, and deletion operations. It is commonly used in various algorithms and data structures, including binary search trees and heaps.