NIX is probably the most advanced package manager out there, it is very good to manage library dependencies, this means that these packages can run much more likely between upgraded or downgraded systems.
To use them in a Debian based system just run:
sh <(curl -L https://nixos.org/nix/install) --no-daemon
Or, if you want to install things system-wide (multi-users), do instead:
sh <(curl -L https://nixos.org/nix/install) --daemon
Finally, update the packages:
nix-channel --update
That's all, now close the terminal and open a new one.
To install a package, you can go do their website to search for a specific package where is 80k packages available and search for a desired one, click the nix-env install option and select the 'Non-NixOS system', that's the command you need to run it to install a desired package.
Examples:
nix-env -iA nixpkgs.flowblade
nix-env -iA nixpkgs.sublime4
nix-env -iA nixpkgs.neovim
nix-env -iA nixpkgs.nodejs
nix-env -iA nixpkgs.netsurf
nix-env -iA nixpkgs.palemoon
nix-env -iA nixpkgs.chromium
Using NIX packages is good if you want to use a specific software that is not available on Debian or if you want to use a more updated version of it
BONUS: If you are using Elive, NIX packages are kept among reinstallations 
TODO / HELP: This howto is really short but NIX is very powerful, you are welcome to add more contents to this Howto as useful NIX commands or features
...... hadn't even noticed we didn't have a HowTo.
