That varies depending on the type of hardware/device/software. The Windows desptop is a type of interface itself being a graphical user interface(gui). There are varying types for both ide and sata drives namely being where the cable plugs into a board as well as controller cards for RAID, SCSI, and Serial ATA arrays. http://www.pcguide.com/ref/hdd/perf/perf/ext/ifSpeed-c.html
There are non pc as well as pc type interfaces like the setup menus seen on your tv or vcr for adjustments or programing and setting up time and date. Being this is in the laptop section portables seen printer and vga/usb ports being interfaces there.
1394 firewire also sees an interface. Your gaming system PS/2, X-Box, X-Box 360 sees interfaces. I readily agree with OMEGA on definitely being far more "specific" if you have something particular you are asking about.