According to Wikipedia:
In computer science, a tree is a widely used abstract data type (ADT)—or data structure implementing this ADT—that simulates a hierarchical tree structure, with a root value and subtrees of children with a parent node, represented as a set of linked nodes.
A tree data structure can be defined recursively (locally) as a collection of nodes (starting at a root node), where each node is a data structure consisting of a value, together with a list of references to nodes (the "children"), with the constraints that no reference is duplicated, and none points to the root.
Alternatively, a tree can be defined abstractly as a whole (globally) as an ordered tree, with a value assigned to each node. Both these perspectives are useful: while a tree can be analyzed mathematically as a whole, when actually represented as a data structure it is usually represented and worked with separately by node (rather than as a set of nodes and an adjacency list of edges between nodes, as one may represent a digraph, for instance). For example, looking at a tree as a whole, one can talk about "the parent node" of a given node, but in general as a data structure a given node only contains the list of its children, but does not contain a reference to its parent (if any).
A tree is a nonlinear data structure that is used to store data in a hierarchical manner. Tree data structures are used to store hierarchical data, such as the files in a file system.
A tree is made up of a set of nodes connected by edges. Special types of trees, called binary trees or binary search trees, restrict the number of child nodes to no more than two.
A tree can be broken down into levels. The root node is at level 0, its children are at level 1, those nodes' children are at level 2, and so on.
A Tree is like a linked list, except it keeps references to many child nodes in a hierarchical structure i.e, each node can have no more than one parent. The Document Object Model (DOM) is such a structure, with a root html node that branches into the head and body nodes, which further subdivide into all the familiar html tags. As an in-memory representation of the DOM, React’s Virtual DOM is also a tree structure.
Take a look at the following tree:-
A simple unordered tree; in this diagram, the node labeled 7 has two children, labeled 2 and 6, and one parent, labeled 2. The root node, at the top, has no parent.
| Operation | Complexity |
|---|---|
| Access |  |
| Search | |
| Insertion | |
| Deletion | |