THis tutorial is meant for those who are aware of dynamic and static urls if you are unware of that do follow the this article
http://www.webconfs.com/dynamic-urls-vs-static-urls-article-3.php on difference betwen dynamic and static urls
Pros of Dynamic URLs they're usually longer?
Google (1 of the 4 major search engines) says they can effectively crawl and index them
Cons of Dynamic URLsLower click-through rate in the search results, in emails, and on forums/blogs where they're cut and pasted
A greater chance of cutting off the end of the URL, resulting in a 404 or other error when copying/pasting
Lower keyword relevance and keyword prominence
Nearly impossible to write down manually and share on a business card or read over the phone to a person
Challenging (if not impossible) to manually remember
Does not typically create an accurate expectation of what the user will see prior to reaching the page
Not usable in branding or print campaigns
Won't typically carry optimized anchor text when used as the link text (which happens frequently due to copying & pasting)
Pros of Static URLs (mostly the opposites of the above)
Higher click-through rates in the SERPs, emails, web pages, etc.
Higher keyword prominence and relevancy
Easier to copy, paste and share on or offline
Easy to remember and thus, usable in branding and offline media
Creates an accurate expectation from users of what they're about to see on the page
Can be made to contain good anchor text to help the page rank higher when linked-to directly in URL format
All 4 of the major search engines (and plenty of minor engines) generally handle static URLs more easily than dynamic ones, particularly if there are multiple parameters
Cons of Statics URLsYou might mess up the rewriting process, in which case your users and search engines will struggle to find content properly on your site.
So - bottom line - dynamic URLs don't afford you the same opportunity for search engine rankings, usability or portability that rewritten, keyword-optimized URLs do. Just because one of the engines doesn't have trouble crawling them doesn't mean it's any less critical to continue optimizing this element of a site's structure.