Linear Data Structure

Data structure where data elements are arranged linearly where each and every element is attached to its previous and next adjacent is called a linear data structure. In linear data structure, single level is involved. Therefore, we can traverse all the elements in single run only. Linear data structures are easy to implement because computer memory is arranged in a linear way. Its examples are arraystackqueuelinked list, etc. 

Elements are accessed in a sequential order but it is not
compulsory to store all elements sequentially. Examples: Linked Lists, Stacks and

Non-Linear Data Structure

Data structures where data elements are not arranged sequentially or linearly are called non-linear data structures. In a non-linear data structure, single level is not involved. Therefore, we can’t traverse all the elements in single run only. Non-linear data structures are not easy to implement in comparison to linear data structure. It utilizes computer memory efficiently in comparison to a linear data structure. Its examples are trees and graphs.  

Elements of this data structure are stored/accessed in a
non-linear order. Examples: Trees and graphs.