The default Plain Permalink also called the Ugly Permalink looks like this:
http://example.com/?p=N
with p as the parameter and N is the unique ID of the post or page in the database.
WordPress comes preinstalled with this setting. It works on all server environments. It is not user-friendly and also not optimized for search engines.
Pretty Permalinks
Pretty Permalinks are SEO-friendly and attractive. They usually contain several words such as the title of the post or page, post category, tag name, etc. You can use Keywords in the URL to make your content readable by search engines.
Pretty Permalinks also help others get an understanding of what the content of the page or post is by reading the URL.
Pretty Permalinks look like this:
http://example.com/2012/post-name/
()