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.
By default permalinks structure looks like:
However, there is possible to have a more readable permalinks, e.g.
Go to Settings > Permalinks and select other kind of permalinks structure.