New nixos user with a question

Help
1

hi new nix user here with a new installation nixos 24.11
I have a question about my new machine, there is a folder in home/user that I can’t figure out where it came from, I think it first appeared after an addition in “sudo nano /etc/nixos/configuration.nix”
and “sudo nixos-rebuild switch --upgrade” but I’m not sure. is there an explanation for this folder

-rw-r--r--  1 user users   45 10 maj 18:04 .nix-channels
drwxr-xr-x  2 user users 4096 11 maj 08:59 .nix-defexpr
lrwxrwxrwx  1 user users   44 11 maj 09:34 .nix-profile -> /home/user/.local/state/nix/profiles/profile
lrwxrwxrwx  1 root root    88 11 maj 18:22 result ->/nix/store/hjnbih8g0z14ssgyc75nr36a25x720w3-nixos-system-nixos-24.11.717822.0c0bf9c05738
2

You mean nix-defexpr?
https://nix.dev/manual/nix/2.25/command-ref/files/default-nix-expression

3

The result symlink came from running nixos-rebuild build (instead of switch or boot). In fact, any nix-build command will produce such a symlink, it’s just there for convenience to point at whatever you just built. You can safely remove the result symlink.

4

yes that is it, thanks for the answers.
as a new nix user is ther one thing I should have in my configuration.nix file