Please explain what this does?

var num1,num2,num3,num4,whole,hi,lo,x,hold,count : integer;
    wholes,num1s,num2s,num3s,num4s,His,Los,pali:string;
begin
wholes:=edit1.text;
listbox1.Clear;
count:=0;

for x:=1 to 4 do
insert(copy(wholes,1,1),pali,1);

if ((strtoint(edit1.Text) > 1000) and (strtoint(edit1.Text) < 9998)) and ((wholes <> pali)) then
repeat
count:=count+1;


insert(copy(wholes,1,1),num1s,1);
insert(copy(wholes,2,1),num2s,1);
insert(copy(wholes,3,1),num3s,1);
insert(copy(wholes,4,1),num4s,1);

num1:=strtoint(num1s);
num2:=strtoint(num2s);
num3:=strtoint(num3s);
num4:=strtoint(num4s);

for x:=0 to 6 do
begin
        if num1<num2 then
        begin
        hold:=num1;
        num1:=num2;
        num2:=hold;
        end;

        if num2<num3 then
        begin
        hold:=num2;
        num2:=num3;
        num3:=hold;
        end;

        if num3<num4 then
        begin
        hold:=num3;
        num3:=num4;
        num4:=hold;
        end;
end;

num1s:=inttostr(num1);
num2s:=inttostr(num2);
num3s:=inttostr(num3);
num4s:=inttostr(num4);
his:=num1s+num2s+num3s+num4s;
los:=num4s+num3s+num2s+num1s;

hi:=strtoInt(his);
lo:=strtoInt(los);
whole:=hi-lo;
wholes:=inttostr(whole);
listbox1.Items.Add(inttostr(count)+': '+his+' - '+los+' = '+wholes);

//showmessage(his+' - '+los+' = '+wholes);
num1s:='';
num2s:='';
num3s:='';
num4s:='';
until whole=6174
else
showmessage('Please try again, the number you typed in cannot be less than 1001 and the values cannot be al the same. eg 1111 or 2222');
end;