Permalinks are the permanent URLs to your post. In WordPress, you have the option of choosing what style of permalinks you would like to use. My suggestion is to ALWAYS use the date and name based option for your posts. Why? SEO of course! When you have the title of your post listed in the URL your post will do better in searches. Here are the options in WordPress:
WordPress will need to access your .htaccess file in order to update the rewrite rules. Make sure that WordPress can access this file or you will get an error.
[...] The post slug is how WordPress cleans up your post title, IF you are using the date and name based Permalinks. Your post title is not allowed to have commas, quotes, apostrophes and other non-HTML characters. [...]