Please refer to the following URL to know the differences between URL and URI,http://onlydifferencefaqs.blogspot.in/2012/08/difference-between-url-and-uri.html

URL:- A URL (Uniform Resource Locator) is the address of some resource on the Web. A resource is nothing but a page of a site.
There are other type of resources than Web pages, but that's the easiest conceptually.  

URI:- A URI is a unique identifier to usually a namespace.
Though it looks like a URL but it doesn’t have to necessarily locate any resource on the web.

URI is a generic term. URL is a type of URI.