A tree is a non-linear data structures in which each node can point to a number of nodes. A tree can be used to represent the hierarchy of data in graphical form.
In trees, the order of elements is not important. If ordering is required then linear data structures should be used like an array, linked list, stack etc.
There are some trees other than this also but these are the most common trees and the type of trees marked with * are the most important one.
All the trees have their specific way of inserting, deleting data and for other operations also. So we will be talking about them in their specific sections.