1. A physical connector that mates with another connector (usually a type of plug on the end of a cable) to electrically connect two devices.
For example, a charging port connects a phone to a power source to recharge the battery. A data port allows a phone to connect to a PC or other device for various types of data transfer.
Also called a "jack" or simply "connector".
2. The act of "porting", or transferring, a phone number from one carrier to another.
See: Number Portability