what is the difference between id and class?

Question

I know the basic use from examples but I still don't fully understand the difference

Answer 1

when u want to style a class element it is styled with a element.class_name
whereas
when styling an element with some id it is styled with a #id_of_element

and

id is unique for an element i.e. there can not be two or more elements with same id_name

whereas

we can use same class name for different elements

and
classes are usually created for a section of the web page

Answer 2

id can be used I only once. class can be used over and over again