Ski touring covers a wide spectrum and there is an ever increasing range of gear which goes with it. Below is a basic guide to the different forms, with their more usual designations.
Low-level skiing on narrow light-weight skis, with no metal edge. Boots are trainer-type shoes, with a bar built into the toe which clips onto the binding on the ski. Abroad, such as Norway or Austria, tracks in the snow are made by a machine, and the skis run in the tracks. Here, tracks are rarely cut, Glenmore Forest and Clashindarroch, when conditions allow). Progress is by a sort of bouncing run, with long poles to help you push. Being lightweight, it can be fast, but you can also go at your own speed.
Effectively hill-walking with skis. The skis are heavier, with a sharp metal edge. Boots are either a heavy leather “walking-boot” type or a plastic boot, with plenty of flex. The ski binding can be either a clip which holds the front of the toe (of the boot) or a cable binding, which has a wire which goes round the heel of the boot. In Scotland, you would normally have “skins” which are like long strips of velvet which you stick to the bottom of the skis. These enable you to walk up a snow slope, with your skis on, you then take them off to ski the downhill bits. In Norway, where the snow is colder and dryer, and the hills tend to be less steep, wax is applied to the base of the ski, which allows enough grip on the snow to progress uphill, but will also slide over the snow when you ski downhill. Poles are shorter and stronger than for cross-country. In suitable snow, all the normal downhill turns – snow-plough, stem, parallel – are possible on Nordic skis, as well as the iconic telemark turn (the one where you go down on one knee).
This is skiing focussed on using the Telemark turn. Modern telemark skis are often heavier than for traditional Nordic, are wider, softer and more curved to help in quick rythmic turns. Modern bindings are heavier, releasable and have riser plates under them. New boots are plastic, taller and with more of a forward angle to them, but with a walk mode to make them better for walking in. Poles would be more like downhill poles.
This is alpine touring – enabling skiing on steeper slopes. The equipment is heavier again, more like downhill skiing. The boots would be a stiff plastic boot with vibram sole, with a ski mode and walk mode, and capable of a rigid crampon. The bindings are releasable, and have an adjustment which can be flipped up to support the heel of the boot when climbing. The peg is put down again and the heel clipped down to the binding for downhill skiing. A ski-crampon called harschisen can be used to cross and ascend hard ice.