Is it possible to communicate with a Serial Port either built-in to my computer or a Virtual Serial Port (USB-to-Serial adaptor) from MATLAB? If yes, where can I find more information regarding serial communication from MATLAB?
You can use MATLAB to talk to your computer's serial port on any of the MATLAB's supported operating system. All the details on how to do so can be found on this documentation page. The documentation explains how to connect, configure, communicate (read and write) and control the serial port.
As for the Virtual Serial Ports - such as a USB-to-Serial adaptor. Most such USB adaptors (dongles) should show up and work as a serial port in MATLAB.
A word of caution though that not all USB-to-Serial adaptors (and their drivers) emulate an on-board serial port exactly. The better the adaptor emulate the on-board serial port, the better performance (reliable and robust) you will get.
Note: When using virtual serial ports remember to restart MATLAB, once you plug in the adaptor, for the new port to show up in MATLAB. This is to allow the underlying serial API to update the list of available serial ports.
In case you would like to read more on serial port, the MATLAB online documentation has a really nice chapter on serial port overview.