**What Is Called Tree in Data Structure?**

A __tree__ is a widely used data structure in computer science that represents hierarchical relationships between elements. It is composed of nodes connected by edges, with a single node known as the __root__ serving as the starting point for traversing the tree.

## Tree Terminology

Before diving deeper into trees, let’s familiarize ourselves with some key terminology:

__Node:__Each element in a tree is called a node. Nodes can contain data and have connections to other nodes.__Edge:__The connection between nodes is known as an edge.It represents the relationship or link between two nodes.

__Root:__The topmost node of a tree is called the root. It serves as the starting point for traversing the tree.__Parent:__A node that has one or more child nodes is referred to as a parent node.__Child:__Nodes directly connected to a parent node are called its child nodes.__Sibling:__Nodes that share the same parent are known as sibling nodes.

## The Tree Structure

A tree structure consists of levels and branches. Each level contains nodes, and branches represent connections between these nodes. The hierarchy of levels determines how elements are organized within the tree.

The first level, which contains only the root node, is referred to as level 0. Nodes directly connected to the root form level 1, their children form level 2, and so on.

### Types of Trees

There are various types of trees, each with its own characteristics and applications. Some common types include:

__Binary Tree:__A binary tree is a tree in which each node has at most two children, known as the left child and the right child.__Binary Search Tree (BST):__A binary search tree is a binary tree that follows a specific ordering property. For any given node, all nodes in its left subtree have values less than the node’s value, and all nodes in its right subtree have values greater than the node’s value.__Balanced Tree:__A balanced tree is a type of tree where the difference in height between the left and right subtrees of any node is limited.This ensures efficient searching, insertion, and deletion operations.

__B-tree:__A B-tree is a self-balancing search tree commonly used in databases and file systems. It allows efficient access to large amounts of data stored on disk.

## Tree Traversal

Tree traversal refers to visiting each node in a tree exactly once. There are several ways to traverse a tree:

__Inorder Traversal:__In an inorder traversal, nodes are visited in ascending order (for binary search trees).__Preorder Traversal:__In a preorder traversal, the root node is visited first, followed by its left subtree and then its right subtree.__Postorder Traversal:__In a postorder traversal, the root node is visited after its children have been visited.__Level Order Traversal:__In a level order traversal, nodes are visited level by level, starting from the root.

## Applications of Trees

Trees have various applications in computer science and beyond. Some common use cases are:

__File Systems:__File systems often use tree structures to organize directories and files.__Hierarchical Data Representation:__Trees provide an intuitive way to represent hierarchical relationships, such as organization charts or family trees.__Database Indexing:__B-trees are commonly used for indexing large amounts of data in databases.__Artificial Intelligence:__Decision trees are employed in machine learning algorithms for classification and regression tasks.

In conclusion, a tree is a fundamental data structure that represents hierarchical relationships between elements. Understanding trees and their various types, traversal methods, and applications is crucial for efficient problem-solving in computer science.