Reason behind using double quotes in font family in CSS?

Question

I want to know what is the reason behind when we use font in font family, but sometimes are single font name have double quotes other have not why? if anyone can help me then please answer my question And if you like my question please upvote my question..

Answer 1

whitespace are use for seperating a different value that can work in same context/rule. like for example

border: 1px solid black

see the space between 3 different value there for 3 different purpose.

now what happen in font family is
font-family: arial black, serif

the browser will see arial and black as 2 different value. thats where double quote comes in. to tell that this 2 piece of code Arial and black should be seen as one