Directories or folders are like drawers that you keep your socks in. They are kept nice and tidy and out of the way.
Your home page (index.html or home.html) is you waiting to go out but you need to put some socks on.
So someone tells you to open the yellow drawer and you will find your socks. You are being 'referred' to the drawer.
The web page needs to know where to be referred to to find the pictures and music files. You tell it the horse picture is in the red drawer or in computery htmlspeak you put 'reddrawer/horsey.pic' or more likely 'images/horse.jpg' .
You need to put in your HTML where your images or music files are. So with all of your pictures in an 'images' directory those lines which are :-
need to be
Of course you need to use your ftp/ssh/web software to create the 'images' directory first and then put all the image files into it. Your starting point would be where your first web page (index.html ?) is, which is called the 'web root directory'. Likewise you could create a 'music' directory for your music files.
See, your house is much tidier because you have put all your socks out of view into your drawers. But... you know where they are.
Inside the two directories (sometimes called folders because it is less to type) you would have your various media files for your web pages to 'drawer' on!!