What is a linear search?
A linear search is also known as a sequential search that simply scans 
each element at a time. Suppose we want to search an element in an array or list;
we simply calculate its length and do not jump at any item.

Complexity of Linear search:-
As linear search scans each element one by one until the element is not found.
If the number of elements increases, the number of elements to be scanned is also
increased. We can say that the time taken to search the elements is proportional 
to the number of elements. Therefore, the worst-case complexity is O(n).

What is a Binary search?
A binary search is a search in which the middle element is calculated to check
whether it is smaller or larger than the element which is to be searched. 
The main advantage of using binary search is that it does not scan each element 
in the list. Instead of scanning each element, it performs the searching to the 
half of the list. So, the binary search takes less time to search an element as 
compared to a linear search.

The one pre-requisite of binary search is that an array should be in sorted order,
whereas the linear search works on both sorted and unsorted array. The binary search
algorithm is based on the divide and conquer technique, which means that it will 
divide the array recursively.