Pingbacks are the comments created whenever one blog is linked to another and enable pingbacks. These are in fact the remote comments.
Something is being posted by a person on the blog. Another person posts something on his blog that is linked to post of some other person. When this occurs a pingback is automatically sent to the first person when both persons have blogs with enabled pingbacks. In order to create pingback, all that is required is to link to someone else`s blog post. In case of that post having pingbacks enables, blog owner sees an appearance of pingbacks in the comments section which they can then approve.