Communication modules are modules used to represent/control ways of communication between the Smoothieboard and the rest of the world. This can be for example a UART or USB serial port.
For a list of communication modules and documentation on their use and configuration, please look at the list on the homepage.
On linux machines the output of the serial debug port is not nicely formated because the smoothieboard sends only a LF but a CRLF is needed.
picocom offers a parameter to fix that:
picocom -b 115200 /dev/ttyUSB0 —imap lfcrlf