Why the html element has two classes

Question

it is often accepted that a html element contains a class but in the jquery two classes were added which is not clear enough. though, what is the purpose of two classes for a html element

Answer 1

Don't get it twisted with the class thing in html and jQuery cos they two different packages.
Html class is just like hypertext reference to different classes created in its CSS style.
JQuery classes are like tools used for instantiation by an object reference.
Go back to basics and learn more bro..