How are electronics made water resistant or waterproof, even when they have perforated or moveable parts (i.e. like a phone )?

Question

How are electronics made water resistant or waterproof, even when they have perforated or moveable parts (i.e. like a phone )?

In:

Answer 1

specially on iPhones or other smartphones all the removable parts such as the SIM tray are covered with rubber band like little rubbers, and the holes and speakers parts have some very thin grills which water cant pass thru. and behind the screen there are a black adhesive.