phase calculation and plot

can anyone please help me understand this function...m new to matlab

function y=folding(x,p,c);

if nargin==2,

   c=1;

elseif nargin==3,

   % do nothing

else

   error('Illegal number of input arguments');

end

jd_col = length(x(1,:)) + 1;

y = zeros(length(x(:,1)),jd_col);

TEMP = x(:,c);

r = TEMP;

TEMP = TEMP./p-floor(TEMP./p);

y = x;

y(:,c:c) = TEMP;

y(:,jd_col) = r;

y = sortrows(y,c);