A pistol grip ski pole has a T-shaped handle with a shelf that your palm rests against, similar to how you'd hold a pistol. This design gives you excellent leverage for pushing off, making it a favorite among Nordic and cross-country skiers who rely on powerful pole strokes for propulsion.
Pistol grips also work well for some backcountry touring, where that secure, locked-in feel helps during long uphill slogs. The palm shelf keeps your hand from slipping, even when you're working hard.
However, pistol grips aren't the best choice for most alpine resort skiing. The same secure grip that's great for touring can make it harder to quickly release the pole during fast pole plants—something you do constantly in moguls, tight trees, or quick turns. If you primarily ski inbounds at the resort, a standard or ergonomic grip is usually a better fit.