The Mole Machines are used for Dark Iron Dwarfs because of their racial ability "Mole Machine". This ability allows Dark Iron Dwarf players to teleport to Stormwind, Ironforge or the Dark Iron Dwarf area Shadowforge City, but there's also 16 secret location that can be collected and added to the Mole Machine.
The secret Mole Machines are hidden all around Azeroth, Outland, and Draenor, and you unlock the ability to teleport to it permanently after physically going to the location and interacting with the Mole Machine there. So visit each of the locations once, and you can teleport there with your Mole Machine as often as you want.
The easiest way to get them all is to install the two addons TomTom and Paste, and add the following macro:
/way The Hinterlands 13.44, 46.72
/way Blackrock Mountain 33.23, 25.10
/way Blasted Lands 62.00, 12.81
/way Un'Goro Crater 52.95, 55.92
/way Southern Barrens 39.10, 9.32
/way Mount Hyjal 57.20, 77.10
/way Blade's Edge Mountains 72.49, 17.63
/way Shadowmoon valley:Outland 50.75, 35.29
/way Icecrown 77.00, 18.67
/way Dragonblight 45.32, 49.90
/way Valley of the Four Winds 31.49, 73.61
/way Kun-Lai Summit 57.70, 62.81
/way Gorgrond 46.69, 38.69
/way Nagrand:Draenor 65.76, 8.27
/way Highmountain:Broken Isles 44.66, 72.90
/way Broken Shore:Broken Isles 71.73, 48.06
After using this macro, just fly to the locations the TomTom add-on tells you to, and you will unlock them all.