NAM is essentially a virtual snapshot of a piece of gear, could be an amp or a pedal that can’t be created and shared by users.
It can’t do modulation, time based effects etc right now, it’s mostly just preamps and drives etc. They’re typically very realistic in how they react and allow you to share gear captures of gear that might be hard to obtain.
Its just a snapshot of the gear with a specific set of controls though, the block has some gain, eq, and volume controls but they’re not necessarily going to respond the same as the actual gear would so you really have to create multiple captures of the gear with different settings.
They’re well worth experimenting with, in my experience a good capture can sound excellent. Particularly when you want to experiment with stuff that’s a bit off the beaten track.