Final answer:
The most commonly used port type for connecting input and output devices to a computer is the USB port. It's versatile and supports a wide array of devices, far more than HDMI, Ethernet, or VGA ports which serve more specific purposes.
Step-by-step explanation:
The port type most commonly used to connect input and output devices to the computer is the USB port (Universal Serial Bus). USB ports are highly versatile and can be used to connect a wide range of devices including keyboards, mice, printers, external storage drives, smartphones, and many other peripherals. Unlike other ports like HDMI (High-Definition Multimedia Interface) which is mainly for video and audio output, Ethernet for network connections, and VGA (Video Graphics Array) primarily for video output, USB ports facilitate both input and output functionalities, making it the go-to interface in most computer setups.