Class class and ID selector (. And #) in CSS)

in the previous days, the interview asked me if I could set the # number in CSS. I am not sure if I can use the # number. I will post it now.

use the class selector class and the identifier selector id to define the selector. The benefits are:
depending on the class or ID, you can express the same HTML element differently.
in CSS, the class selector is in a halfwidth English sentence ( . , the ID is prior to halfwidth English well number ( # .
example of a class: # top { background-color: # CCC; padding: 1em }< br> ID: . intro { color: red; font-weight: bold; }
call CSS connection attributes in HTML id and example of class :

id = "TOP"

chocolate curry

class = "Intro" This is my recipe for making curry purely with chocolate

class = "Intro" Mmm Mmmmm

the difference between ID and class is that ID is used on unique elements, while class is used on more than one element.