NTN stands for New Telemark Norm, and yes—it's specifically for telemark skiing. Unlike traditional 75mm telemark setups that use a duckbill toe and cable binding, NTN uses a completely different boot sole interface without the duckbill. The boot engages with the binding more like an alpine boot does, rather than slotting into a toe iron.
The big advantage of NTN over older 75mm systems is significantly better lateral control and edge power while free-heel skiing. If you've ever felt like your telemark turns were sloppy on hardpack, NTN addresses that directly. However, NTN boots only work with NTN bindings—they're not compatible with alpine bindings or 75mm telemark bindings.
If you're not planning to telemark, NTN isn't relevant to your setup at all. But if you want modern, responsive free-heel performance, it's the way to go.