Is FirstNet a cellular network?

Excuse me, could you please clarify for me if FirstNet is indeed a cellular network? I've been hearing about it recently, but I'm not entirely sure of its exact nature. Is it a dedicated network specifically designed for a certain purpose, or is it simply another addition to the already existing cellular networks? And if it is a cellular network, what sets it apart from the others and what makes it unique? I'd really appreciate it if you could provide me with a clear and concise answer to these questions.