Why Bare Skin Matters
Most modern phone screens are capacitive touchscreens. The glass has an invisible grid of conductors woven into it, and a small electric field hovers across the surface. A bare finger interferes with that field because the human body is mildly conductive — your skin and the salty water inside you can carry electricity. When a fingertip touches the glass, it pulls a tiny amount of charge away at that exact spot, like a small leak in the field.
Pinpointing the Touch
The phone's controller chip is constantly watching that grid of conductors for any change. When the field dips at a particular intersection of the grid, the chip reads off the coordinates of that intersection and reports a touch event to the software running on the phone. The screen does not actually feel pressure at all; it is mapping a change in electrical behavior to a position. That is why a very light tap works just as well as a firm one, and why you can sometimes draw on a screen with your knuckle but not the back of a fingernail.
The Glove Problem
This also explains the everyday glove problem. Most fabric gloves act as an insulator between your skin and the glass. The conductive part of you — your finger — never gets close enough to disturb the screen's electric field, so the screen sees no touch even though you can clearly feel the tap. Special "touchscreen" gloves work because they have conductive threads woven into the fingertips, giving the field something to react to. The same logic explains why a wooden pencil or a plain plastic stylus is usually ignored: nothing conducts, so as far as the phone is concerned, no one is there.
Source
This article was written using information from Wikipedia.