CCD is "charge-coupled device", the sensor in most cameras that converts light to electric signals. You can read about it in more deails here (CCD), here (sensors), and here (sensor size). The 1/1.7 & 1/2.5 I believe you're referring to the sensor size. Generally the larger the sensor the better, as when the pixel size increases the sensitivity of each pixels will also be better, resulting in lower noise output. So in this case 1/1.7" sensor size would be better.