The "public_html" folder is linked to the folder named "www". These two folders are linked and where your website files should sit if you want them to be seen on the internet. Please use the Public_html folder as your default choice of where to store the website.
Please do not delete these folders as this will result in the website not displaying on the internet. If these folders are removed, you can expect to see an error : 404 when visiting your website.
If you have already deleted these folders or one of them, you can use your FTP program or the built in file manager to create a new folder and you name it either "www" or "public_html" -depending on which one was deleted.