wireless messaging application

hi..:) i doing a proj on this wireless messaging application using C#. i cant understand the code as i am weak in this area. i wish that someone out there able to tell me wat does this statements mean... apreciate greatly !! :D

for (i = 1; i <= result.Length; i++)
{
serialData[i + 3] = Convert.ToByte(System.Convert.ToInt32(result[i - 1]));
}

//Calculates the 8 bit checksum
intCheck = 0;

for (i = 0; i <= result.Length + 4; i++)
{
intCheck = intCheck + serialData[i];
intCheck = intCheck & 0xFF;
}
if (intCheck > 127)
{
intCheck = intCheck ^ 0xFF;
}