The Pi has an HDMI port for video. It has sound and a mini usb to which you can connect a USB hub through which you attach mouse a keyboard, externsal HDD, WIFI and virtually anything else that takes your fancy.

The idea though, is that they be incorperated into other technology, especially for the IOT. There are some interesting YouTube vids on this kind of inovation, already happening, along with many other such tiny computers
These are not the only ones out there by any means.