What does views UI Module do? I'm new to drupal and I have read about view UI module in many places but was not able to find what exactly it is.Can any one help me on this ?
Views UI module gives you a nice user interface to create, and edit your views.
A "view" here means what the Views module produces; it could be a slideshow, a page with a table, a block of recent comments, etc. 

You can turn that module off if you have finished making all the views, and the site is ready to go on production. Your views will work no matter you have the Views UI module enabled, or not.