Smartphones are expensive — you wouldn't want to spend up to $1,000 or more and end up with a scratched screen. Many people still buy screen protectors to protect their purchase, but are they still necessary with modern display advancements?
Having a big scratch on your phone is like having an itch in your brain you just can't reach. Plus, it lowers the resale value of the device when you want to upgrade. A screen protector can keep the surface pristine, but buying one is more complicated than it should be. It's also worth asking if modern phones even need one anymore.
A screen protector is simply a sheet of clear plastic or very thin glass that you adhere to your smartphone's screen. The protector is cut to fit the exact shape of your device along with cutouts in the appropriate places - that's why you buy different screen protectors for different devices.
The glass on your gadgets has gotten a lot more scratch-resistant since the days of the iPod. Corning's Gorilla Glass will not scratch if you rub it with your keys or loose change, which is a big step forward.
Many materials can be used for a screen protector.
Polyethylene Terephthalate (PET)
PET is a type of plastic usually found on things like water bottles and food containers. PET screen films provide the least amount of scratch- and impact-protection, but they're super cheap, light, and thin, and as a result are less visible once applied to your phone.
When you think of the screen protectors of old, you're probably thinking of TPU. TPU screen protector is a flexible plastic that's a huge hassle to install (it involves using a spray solution and squeegeeing out lots of bubbles), doesn't feel very smooth (thanks to its almost rubbery texture), and adds an "orange peel" type glare to your phone's screen. Still, it's flexible, so it can go edge-to-edge on any phone, it has better impact protection than PET, and it has limited "self-healing" powers for small scratches.
On the other hand, it comes in a few different styles depending on the look, feel, and features you want, for example there are TPU clear screen protector, TPU matte screen protector and so on. However, not all styles are available for all phones, and some phones don't have TPU options at all.