If you don't already know the benefits it's unlikely it solves a problem you have.
Even among its users many are using it because it's cool rather than because they actually need it.
It's a declarative system, meaning you can describe how it should be setup (using a magic strings you have to look up online) and then it "sets up itself" according to the description.
It's normally something you'd use for mass and/or repetitive deployments.
It's usefulness for a single system is debatable, considering you can achieve very close to 100% of "reproducibility" anyway by copying /home and /etc and fetching a copy of the package list.
Where the prescriptive approach is supposed to help is when you attempt to reproduce the system a long time later, after things like config files and packages have changed. But it doesn't help with /home, it hasn't been tested over long intervals, and in fact nobody guarantees long term compatibility for Nix state.