So instead of having a URL that looking like this:
http://something.com/?blah/7856?/
You will have a URL that looks a little like this:
For posts: http://something.com/2009/2/post/
For pages: http://something.com/folder/page/

After you log on to your WP admin, on the dashboard you’ll find a “Settings” link on the left sidebar. Once you click it, on the same sidebar, under Settings you’ll find something called Permalinks.

Click on it, and it will take you to a page and if you read through, it will tell you a little about these Custom URLs or as I like to call them Simple URLs. So here you can basically change your URLs and customize them so that they can look a little more simple.

As you can see above, I have chosen the third setting Month and name which means that my URL will have a month and a post name after my site’s name. But you can choose anything you like. You can also make up your very own setting, all you need to do is select “Custom Structure” where you can manually change the URL’s to whatever suits you. If you need to know some more tags other than those given, just click on the link on the top of the page where it says Number of tags are available, this link will lead you to a WP Codex page which explains more about the tags you can use for your custom URLs.

After you have chosen the setting you want, click on the Save Changes and WP will automatically change ALL your post and page URLs to the setting you have chosen.

That’s about everything you need to know about post URLs. If you have any questions, feel free to ask me on a comment.