how does the <aside> tag work

Answer 1

It does not do anything on its own, is just a box. You have to move / style it with CSS on your own. It's general purpose is to add additional information, which is not in the primary focus, "aside" the "main content". You should use it like this and style it to fulfill this (e.g. as box appearing on clicking a plus or info sign or as a smaller part on the right side for desktop view).

Answer 2

it is just a structural tag in html 5
like(header,main,article,aside,section,footer) .
these are functionaly just like div but help alot while understanding your code structure to you and other.