What is oleophobic coating?
Oleophobic coating make your phone screen smudge resistance. Smudge resistance means dirty stuff like grease will not stick permanently on it. A simple wipe with soft cloth can make your phone looks new. Without oleophobic coating, grease will just spread around when you wipe it with soft clothes. That makes you have get some cleaning solution to clean it off.
It's also used on car windscreen. You will feel it when you drive in rain and the rain water will just slide through. Sometimes it's because of your driving speed but with oleophobic coating, you don't have to drive fast to see the rain water sliding through the side.
Bad news about oleophobic coating is, it will wear off with time. Usually it should be able to last for 2 years but if you misuse it, or if the oleophobic coating quality is bad, it will wear off in just few months.