Please refer to the INDEX () in Help.

(1)  Please scroll down and take a look at the third example of Reference
form.

=SUM(INDEX(A1:C11,0,3,1))

I don't agree with the following description (result) beside the above
formula.

"The sum of the third column in the first area of the range A1:C11, which is
the sum of C1:C6. (216)"

Please note that the sum of C1:C6 is NOT 216.  So, either C1:C6 is wrong OR
216 is wrong.

My vote is the former.  In my opinion, the first area of the range A1:C11 is
A1:C11 based on the formula, although row #7 is blank.  If we only want the
third column, then we should look at C1:C11.  The sum of C1:C11 **is** 216.

Please let me know what the right version should be.  Either way MS needs to
fix the above description.

(2)  Please compare the following:-

First example of array form =INDEX(A2:B3,2,2)    and

First example of reference form =INDEX(A2:C6,2,3)

Just looking at the formulas I don't see any difference in the format and I
won't be able to tell that one is array form and one is reference form.
Also, they both return a value.  What is Help trying to tell me?

(3)  Array vs. Reference

As far as I am concerned, an array is a reference.  A1:A6 is an array and is
also a reference.  However, A1 is NOT an array but is a reference.  I am
quite confused about these two terms as Help puts it and the fact that
INDEX() is categorized into array form and reference form.  Comments
welcome.

Appreciate help in sorting out the above.

Epinn