USB In addition to the USB 2.0 ports provided on the back panel, most motherboards
will have connectors for additional ports, either on the front of
the case or in a panel that fits where a PCI card might otherwise be
connected. USB 2.0 ports (and be sure that your chosen motherboard
supports the faster 2.0 standard) are used for connecting various peripherals
such as printers, external hard drives etc. USB connectors are also
used for connecting MP3 players, some cameras and an assortment of less
serious devices like fans, nerf missile launchers and drink warmers. Given
the growing popularity of USB devices, the more ports your motherboard
supports the better.
Serial (COM) or parallel (printer) ports Traditional 9-pin serial and parallel
ports are much less used than they used to be. Many motherboards
have dropped the parallel port (formerly used almost exclusively for connecting
printers) altogether, while serial ports, which once numbered as
many as four, are now usually solitary. The principal use for serial ports
was once connection to either a mouse or an external modem, both of these
devices now connect via USB. Unless you are connecting some seriously
old peripheral hardware, these ports will be of minimal importance

IEEE 1394 firewire Firewire ports are principally used for connecting DV
(Digital Video) cameras and external hard drives. This technology got a
foothold because it was much faster than USB 1.0 and 1.1. With the near
ubiquity of USB 2.0, however, the original (and still the most common)
IEEE1394 implementation, firewire 400, was actually a little slower. For this
reason, and in spite of the existence of a faster but seldom implemented
specification, firewire 800, firewire is not as popular as USB. Like USB,
most motherboards that support firewire will have one or more external
ports on the back panel and the ability to connect one or more additional
ports. One or two firewire ports will suffice for most users.
Note that, regardless of the motherboards native support, additional ports
of all kinds can always be added via a PCI or PCI-E 1 card