The selector indicates what HTML element you want to add styling to. The declaration, which is always enclosed in curly brackets, is where you specify how you want the selector to be stylized. The declaration has a property with a corresponding value, and every declaration is closed off with a semicolon.
Comments can be added into a CSS styles sheet in order to provide documentation and explain how the code works. Comments are ignored by browsers, and all comments must begin with "/*" and end with "*/". Comments can span multiple lines, so long as they begin and end with the correct characters. For example:
/* This is a comment */