Hi

WHat are the port in the digital design? Are they referred to input and output? How about clock?

Can anyone please give an explanation or refer some documents?

Thanks

In general, a "port" is a point of connection of a net to the "external world".
The "external world" may be a higher hierarchy level cell/design, or a pad, or a pin of a chip/package.

The term "port" is use din both digital and analog designs.

In layout, "port" is often called "pin", which creates some confusion - because the term "pin" is often used for device instance terminals/pins.