What Are WordPress Pingbacks & Trackbacks?

If you've ever dug into the WP dashboard while blogging you may have come across pingbacks & trackbacks and scratched you head as I have. What are they?  What they do? Should I allow them.

Here's a good article by John Hughes that explains Pings and Trackbacks that does a good job of explaining them and why it's best not to allow them.

https://themeisle.com/blog/wordpress-pingbacks/