A permalink ("permanent link") is a static web address that readers of a blog or news source can use to reference a specific blog post or entry.
Why should you use permalinks? Blogs and dynamic news sources update their content regularly on a main page — called main.html, for example — that often displays only a few of the site's latest updates. If a reader bookmarks the main.html page in his browser, he'll be able to return again and again to the blog's main page, but chances are that the posts will have changed, replaced by newer content. To bookmark a specific entry, the reader must be able to reference a permalink, a static — permanent — link that refers specifically to the post that interested him.
We recommend that you set up permalinks for your blog so your readers can easily link to your posts, helping you drive and retain traffic to your site. You can set up permalinks from your WordPress control panel (learn about managing your blog). From the Settings area of your WordPress console, choose Permalinks to get started.
The Customizable Permalinks plug-in allows you to create easily understandable permalinks based on parameters such as the date or blog post title. WordPress calls these customized, permanent links Pretty Permalinks. Learn more.
Please note that if you move or rename your WordPress files after setting up permalinks, any permalinks already generated for your blog posts will no longer function properly. For this and other reasons, we strongly recommend that you do not move or rename your WordPress files after activation. Learn more.
Learn more about permalinks on the WordPress web site.