May I ask what does .nix files do? I have joined unixporn community,and when I look into the dotfiles of some nix os user,their config are all written in nix rather than .conf or some other prevalent files. Should I learn nix if I want to use nix os? Or can I config my apps such as waybar in a way just like other systems (such as arch)?

I am new to Linux and the concept of “rss”,I have use fluent reader on Linux and feeder for Android to read news which support rss service.However,I still don’t understand what is aggregator and why do I need it? The only thing I have done so far is copy the rss link and paste to my rss reader. Could anyone eli5 to me?