After much of researching i am confused with the difference between url rewriting,pretty url and hiding url...Though all the three almost performs the same functionality, but what is the difference between these three things?which is useful for SEO ? By seeing the URL can we identify whether is it just hiding url or url rewriting?
You seem to have been confused with the numerous terms that have been used in the articles and tutorials you have read.
Hopefully this will help out somewhat:
Pretty URL:
This is sometimes also called a search-engine friendly URL (because that's exactly what it is), and will generally look something like: users/benmajor/profile/ Google now places a lot of weighting on the URL a page is accessed with, so it's a good idea to follow this pattern.
URL Rewriting:
This is the actual technology used to convert a pretty URL into its system counterpart. For example, using Apache's mod_rewrite module, you can easily convert users/benmajor/profile into profile.php?user=benmajor using the following RewriteRule:
RewriteRule ^users/[(.*)]/profile/?$ profile.php?user=$1
URL Hiding:
This one's a little more difficult to answer, since I don't know the context in which it was used, but I'm going to assume that this term simply means to hide the system URL (i.e. profile.php?user=benmajor) from the user.