dpotrf arguments

With the help of this great forum and old post, I was able to finally execute my first example on Cholesky factorization. However, I have a question. I call the function like this:

  dpotrf(&'L',&N, // A is NxN matrix
        A,&N,&nInfo
  );

Since I am planning to do a distributed factorization, I have to be sure about the arguments. What is the latter 'N' used for? My first thought was about the dimension of the output, but that's the same array, so I am confused.

Moreover, the documentation gives this prototype

void pdpotrf (char *uplo , MKL_INT *n , double *a , MKL_INT *ia , MKL_INT *ja , MKL_INT *desca , MKL_INT *info );

In my example, the arguments are less than what the prototype has. Why there are more arguments there?

Finally, I do not understand ia, ja and desca arguments. Come someone explain to a student like me their use?