A permalink is the URL used to link to your content. It should be permanent, and never change. Hence the name permalink.
The default permalink structure in WordPress is
http://www.yoursite.com/?p=xxx
where xxx is an ID that WordPress assigns to your page or post. Now, not only is this ugly and not very user friendly, it’s also not good for SEO because it doesn’t contain readable words.
So, let’s go ahead and change that.
Go to Settings –» Permalinks. Under Common Settings, select Post name and click Save changes.