When you touch a smartphone screen, it reacts quickly. You can press a button, make a photo larger, or type letters.
Many touchscreens read a small change when a finger touches the glass. Because our bodies can carry a little electricity, the screen can find where the finger is.
Inside the screen, there is a thin pattern of lines. When a finger comes close, the electrical state changes in one place. The device checks this change.
Then the device decides, “This place was touched.” That information goes to the app, and the screen changes.
If the screen is wet, it may not work well. Water can also change the electrical state, so the device may become confused.