The same concept can apply to other aspects of your application as well. If you think about a typical blog, the homepage only shows a list of posts. Any comments to those posts are displayed only on a permalink page. Retrieving those comments for any given post can be a potentially painful process, given there can be any number of them. It’s further complicated if the site allows threaded comments because finding and assembling those threads can be intense.
what is a real world example of threaded comments
what is a php example of threaded comments