WordPress – Permalinks

Permalinks are the permanent URLs to your individual weblog posts, as well as categories and other lists of weblog postings. A permalink is what another weblogger will use to link to your article (or section), or how you might send a link to your story in an e-mail message. The URL to each post should be permanent, and never change — hence permalink.

Source: http://socialmediarodeo.com/gunslingers/wordpress-permalinks