What is difference b/w links and i/o ports?

 What is difference b/w links and i/o ports?

Firstly, any thing that physically connects two devices is called Link. For example, a wire (Twisted Pair) connecting two devices acts as a link between two devices.
Secondly, Port is an interface on a computer to which you can connect the input and output devices of your computer. Computers come with multiple ports for connecting mouse, keyboard, monitor, printer and USB etc. Similarly, there are some network ports which are used to connect a computer with other computer or network related devices. For example: Ethernet Port.

So, link is the cable connecting two devices and the port is the interface where you insert the cable in order to connect two devices.