What is the difference between id and class selectors?

Answer 1

You can only have one element with the same id. Let's say one element has id: top-right-logo. there is only going to be one. You don't need more. If you have a class, for example called: section-title, you are probably gonna use that more times than one.

Answer 2

The only difference is the way they're referred to and defined a class selector is reffered to in CSS by a period (.) whereas an id is referred to by a hash sign ( # ) and creating on in HTML for class -> class="class_name", for id id = "id_name"