A-Frame carry attaches your skis vertically on both sides of the pack, with tails at the bottom and tips crossing at the top to form an 'A' shape. You slide your poles through the middle. It's the most popular carry method for ski touring because it keeps weight balanced on both sides of your body, which feels much more stable on steep or tricky terrain.
The big advantage is how natural it feels while hiking—you're not getting pulled to one side, and you can easily grab your skis without taking the pack off. The main downside is that skis stick out on both sides, so they can snag on tree branches in tight glades.
If you're doing any real touring or longer approaches, A-Frame is hard to beat. Just make sure the attachment loops fit your skis—wide powder skis may not squeeze into some smaller packs.