This is vague to the point of being useless, given the Nix expression language is untyped.

A snippet from freeswitch.nix:

      configTemplate = mkOption {
        type = types.path;
        # omitted
      };
      configDir = mkOption {
        type = with types; attrsOf path;
        # omitted
      };

• Where does types come from?

  See NixOS manual at "Option types".

• What is the difference between the path types? (I guess, the second one is attribute set consisting only of paths.)