My dad worked at NASA and built circuit boards that are currently in space. He got confused a few years ago because "how can you have a folder inside a folder

My dad worked at NASA and built circuit boards that are currently in space. He got confused a few years ago because "how can you have a folder inside a folder? Only files get put in folders". Of course, he would not read this book. If someone can't figure out how to make a folder but wants to write HTML, they have a problem this book should t be obligated to solve.