Hello,
You usually use the term "channel" when referring to analog input acquisition or analog output generation.
Now, talking about digital signals, a "digital channel" is considered to be a channel name (like a Virtual channel for one of the digital lines of a certain port).
And a "port", would be a group of digital lines. Digital ports usually have 8 digital lines, but there are times in which a digital port is made up of 4 digital lines. This is the main reason why you usually have to specify a port width along with the port number of your device.
Hope this information helps...good luck!
