When you enable pingbacks, you allow WordPress to send
notifications to other blogs when you link to them in
your content, and vice versa. For example, if you write a
post and include a link to another blog, that blog will get
a pingback notification. They can choose to display this
notification as a comment, showing their readers that you
have linked to their content.
It's a way of acknowledging the source and can help with
networking and building relationships with other bloggers.