There are two console types available in pfSense, VGA and Serial. The active default console depends on the image in use. The difference between the two console types is explained in more detail below.
The VGA console is a console with a traditional monitor and keyboard. The keyboard can be PS/2 or USB. The VGA console requires hardware with a monitor port and either PS/2 or USB ports for the keyboard, or in some cases a serial BIOS that does VGA redirection.
The VGA console is active by default in the full install, Live CD, memstick installer, and NanoBSD+VGA images.
The Serial console uses a serial/COM port to communicate with a serial client. It is primarily intended for systems without a monitor or keyboard, but can be used on systems where those are not usable or preferred.
The serial console is active by default on NanoBSD images, and may be enabled under System > Advanced on full installs.
You will need a null modem serial cable attached between the COM1 port on the firewall and your serial client. A hardware serial port is required on the firewall, but the client may use a USB serial adapter if needed.
Serial clients are quite common, often pre-installed on an operating system or easily available. The free PuTTY client is the most popular choice. Other choices include tip/cu on BSD/Linux, minicom, and Hyperterminal.
The serial port is set for 9600/8/N/1 by default, so set your client software appropriately. On pfSense 2.1 the serial port speed may be changed under System > Advanced.