Matlab problem, need detailed explanation

Write a user-defined function that sorts the elements of a matrix. For the function name and arguments, use B-matrixsort (A), where A is any size (m xn) matrix and B is a matrix of the same size wit rearranged in descending order column after column with the (1,1) element the largest and the (m,n) element the smallest. If available, use the defined function downsort from the previous problem as a su the elements of A bfunction