How is the this code functioning with the help of I, j, and k?

How is i!=j functioning here? what is the role of k here? How is ctr working? can anyone help me understand the concept of this code?

    #include <stdio.h>
int main()
{
    int arr1[100], n,ctr=0;
    int i, j, k;
       printf("\n\nPrint all unique elements of an array:\n");
       printf("------------------------------------------\n");  
       printf("Input the number of elements to be stored in the array: ");
       scanf("%d",&n);
       printf("Input %d elements in the array :\n",n);
       for(i=0;i<n;i++)
            {
          printf("element - %d : ",i);
          scanf("%d",&arr1[i]);
        }
    printf("\nThe unique elements found in the array are: \n");
    for(i=0; i<n; i++)
    {
        ctr=0;
        for(j=0,k=n; j<k+1; j++)
        {
            /*Increment the counter when the seaarch value is duplicate.*/
            if (i!=j)
            {
               if(arr1[i]==arr1[j])
              {
                 ctr++;
               }
             }
        }
       if(ctr==0)
        {
          printf("%d ",arr1[i]);
        }
    }
       printf("\n\n");
}