Any line in a file with '#' is
commented, which basically means as it sounds...it is ignored by whatever actually uses the file. They are either for notes that explain how things work to a person reading the file, sometimes to remove a line, instead of deleting it, you just comment it, in case it breaks something and you want to re-enable it later. Many configuration files come with a number of commented lines that you can 'enable' by just uncommenting.