A permalink is a stable human-readable and search engine-friendly link to your article.
WordPress URL Structure
The default URL structure of WordPress is to append, for example, "/?p=123" to the end of the URL to view article 123. This URL is nice and short, but is difficult for visitors and search engines because it doesn't give any information about the post's content.
Changing Your URL Structure
Visit the permalink settings interface by clicking on Settings and then Permalinks in the WordPress admin panel.
It is not recommended that you change your permalink structure after you have already established your site and audience. Other people may have bookmarked pages on your site or other blogs and articles may have links to your site. Changing your permalink format could cause these bookmarks and third-party links to not work.
Permalink Types
Plain: Use the post ID number in the URL as: ?p=123
Day and Name: Use the date as YYYY/MM/DD and post name
Month and Name: Use the date as YYYY/MM and post name
Numeric: Use just the post's ID number
Default: Use just the post name
Custom Structure: Use WordPress variables to create your own URL structure