What is the difference between a capacitive touch screen and a TFT screen ?

You can not compare the capacitive touch screen and TFT screen directly, since they are two different kinds of components.They can be both found on most of the mobile phones.

A capacitive touch screen is a touch screen that is transparent like glass and does not display anything or emit light. Its function is to sense the user’s touch operation. The picture below shows what a capacitive touch screen is.

The TFT liquid crystal screen is a thin film transistor liquid crystal screen, which is a display screen, and has no function of sensing touch, and can only be used to display the image. The figure below shows a TFT LCD screen.

These two types of screens are usually intergrated on the mobile phones by overlaping them up and down. The TFT LCD screen is designed to dispaly the images, while the capacitive touch screen functions for sensing user operations. This is how the “internal screen” and “outer screen” originates.