Pingback And Trackback

I’ve recently installed WordPress after going through a zillion different blog/CMS packages. It fits what I want perfectly, and it’s all running smoothly!! (at the moment I’m just messing with the layout and presentation 😉 )
My question is simply: What is pingback, and trackback?
I’ve searched but can’t find a definition of what they are, or how they are used.
Please could someone enlighten me. 🙂
Cheers,
Rich.
http://monoecho.com