It notices charge, not pressure
How Does Glass Feel Your Finger?
A touchscreen finds your finger because your body drains charge from a grid of clear wires.
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Step 1 of 5
Pressure is not what the screen notices.
A pencil tip or a woollen glove can press as hard as you like and nothing happens, while the lightest bare fingertip works immediately.
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Step 2 of 5
The screen hides a grid of clear wires.
Above the picture sits a mesh of transparent conductors, rows running one way and columns the other, thin enough that you never see them.
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Step 3 of 5
Your finger steals charge at one crossing.
You are mostly salty water, which holds charge well. Bring that close to a crossing point and some of the charge stored there transfers to you.
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Step 4 of 5
Scanning the grid finds the spot.
The chip energises one row at a time and measures every column, so a dip in the reading pins your finger to a single crossing on the mesh.
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Step 5 of 5
The same trick handles several fingers.
Because every crossing is measured separately, two dips simply mean two fingers, which is what makes pinching and rotating possible at all.
A phone screen scans its entire grid about 120 times a second, which is why a fast swipe still feels like it is glued to your finger.
The short version
The screen never notices pressure — a gloved finger can press as hard as it likes — because what it measures is charge draining into the salty water you are made of. Every crossing is read separately, which is why pinching and rotating work.
Try it yourself
Try your phone with a dry glove, then a knuckle, then a damp fingertip. Only the conductive, slightly wet contacts register.