STN (Super Twisted Nematic) is a type of LCD (liquid crystal display) flat-panel display technology.
CSTN stands for Color Super Twisted Nematic. Both terms can refer to the same type of color LCD display.
STN uses less power and is less costly than TFT technology, but at the expense of image quality and response time.
STN technology is a passive-matrix technology, meaning that each pixel must be "refreshed" individually many times each second. To accomplish this, the liquid crystal must react slowly enough to maintain state between refreshes. This keeps response times relatively low, and limits brightness and contrast.