Circular subarray sum pdf

Can you pl explain the article.Not understood what is circular subarray

Basically in this question, you are given an array, and u have to calculate the maximum circular sum, thus this question can be solved using two cases, firstly if we consider that there is no wrapping, then we will calculate the sum1 based on kadane algo, but if we consider wrapping of elements, i.e we can have array elements to be in circular order, then u will calculate sum simply by reversing the sign of every element of array and then u will use another variable to calculate the sum2 based on kadane algo again, and then larger of these two sums will be your final ans.