Touring/AT Compatible means the ski has a reinforced mounting area specifically designed to handle tech or pin-style touring bindings. These bindings allow your heel to release for walking uphill, which is essential for backcountry travel. The reinforcement matters because touring bindings exert different forces on the ski than standard alpine bindings, and mounting them on a ski not built for it can lead to binding pull-out or damage.
If you're planning to earn your turns in the backcountry, yes, you need this. It's not optional—it's a safety and performance requirement. Without touring compatibility, you simply can't use the bindings that make uphill travel possible.
The good news is many touring-compatible skis can also accept regular alpine bindings, so you can still use them for resort days. Just know these skis may have slightly lighter construction in the mounting zone, so if you're an aggressive resort-only skier who never tours, a standard flat alpine ski might feel more substantial underfoot.