In short: (S)TN is almost always monochrome and in a calculator or Game Boy: just glass, electrodes and liquid crystal. It’s cheap and customizable but it doesn’t scale to high resolutions well and the contrast is poor. TFT (and the later IPS) is almost always color and uses a thin film transistor on each subpixel to hold its state between updates, simplifying driving while maintaining contrast at high resolutions.
In short: (S)TN is almost always monochrome and in a calculator or Game Boy: just glass, electrodes and liquid crystal. It’s cheap and customizable but it doesn’t scale to high resolutions well and the contrast is poor. TFT (and the later IPS) is almost always color and uses a thin film transistor on each subpixel to hold its state between updates, simplifying driving while maintaining contrast at high resolutions.