QwertyWEB

           Permalinks in easy words help in creating permanent links on your blog/websites like wordpress , blogger and many more blogging platforms that are indexed by search engines like google , bing , yahoo etc to categorize posts . Similarly browsers like firefox , IE , safari , opera etc use permalinks to help navigate to your posts. When you hover over a permalink in your browser tab near to the favicon you can read the post name in the status bar . Permalinks is one of the delicate tool which when used in proper guidelines can help improve in traffic to blog  by improving SEO .
According to wiki ,

        A permalink, or permanent link, is a URL that points to a specific blog or forum entry after it has passed from the front page to the archives. Because a permalink remains unchanged indefinitely, it is less susceptible to link rot. Most modern weblogging and content-syndication software systems support such links. Other types of websites use the term permanent links, but the term permalink is most common within the blogosphere .

Blogger automatically generates a permalink based on the title of your post. Permalinks provide information to the viewer about the kind of content being pointed to.
   
The permalink for this Blog Post is:

    http://qwertyweb.blogspot.com/2010/02/polish-permalinks-for-better-seo.html

There is some issue or i better say regulations of blogger , that is when we first write the title of blog post and publish post , the title gets permanent and if again you edit the post and change the title still  permalink remains permanent and nothing can change the link , But if you delete the post and again add new post of desirable title then you can change it , but not without deleting !

Best Example is This link
http://qwertyweb.blogspot.com/2009/07/download-mocrosofts-new-search-engines.html
Here i mistakenly wrote Macrosoft instead of Microsoft , but then i have edited post but still permalink is the same
Benefit is that , i get traffic for even Macrosoft google results coz its still lurking in permalink while its no where in the blog post or Meta ! However google does not consider stuffing so much of useless words otherwise it can be considered as spam ,  mistakes should not be made again and again however , such tweaks can surely improve SEO
Here is another reason to add to differences between Blogger and Wordpress why wordpress is better ( one feature Blogger do not have )
           The issue with Blogger is that it accepts only the first 30 or so characters of your title to create the permalink and the rest is not accepted, so if you do have a longer title you can run into problems but in Wordpress , you can have as many character as you want , not too many , as it too has limits but definitely better and longer than blogger in this feature . So as said before first use a accurate title short and sweet after correctly analyzing what exactly is the blog post all about if you want to avoid losing the end characters from your permalink.
For instance a long title such as the one below would result in a shortened permalink which would lose the important fact that this post is related to working with Blogger:
So this is the title       >>  Get search engine friendly Permalinks for better SEO
and this its permalink >>  http://qwertyweb.blogspot.com/2010/02/polish-permalinks-for-better-seo.html

You can use this Tweak to easily create interesting and professional looking eye catchy and summary short with still memorable and easy short titles.