Question

Will anyone describe IEnumerable and what is difference between IEnumerable and array
and where to use it.. all information about it and how to use it.

Answer 1

An array is a collection of objects with a set size.

int[] array = [0, 1, 2];

This makes it very useful in situations where you may want to access an item in a particular spot in the collection since the location in memory of each element is already known

array[1];

Also, the size of the array can be calculated quickly.

IEnumerable, on the other hand, basically says that given a start position it is possible to get the next value. One example of this may be an infinite series of numbers:

public IEnumerable<int> Infinite()
{
    int i = 0;
    while(true)
        yield return i++;
}

Unlike an array an enumerable collection can be any size and it is possible to create the elements as they are required, rather than upfront, this allows for powerful constructs and is used extensively by LINQ to facilitate complex queries.

//This line won't do anything until you actually enumerate the created variable
IEnumerable<int> firstTenOddNumbers = Infinite().Where(x => x % 2 == 1).Take(10);

However the only way to get a specific element is to start at the beginning and enumerate through to the one you want. This will be considerably more expensive than getting the element from a pre-generated array.

Of course you can enumerate through an array, so an array implements the IEnumerable interface.