What is URL and URI?

URL refers to the protocol(like http:// or ftp:// ) and domain name (http://www.sun.com/) of the requested resource.

Example : http://www.sun.com/
protocol --> http
domain name --> http://www.sun.com/

Here, Domain name(http://www.sun.com/) has been mapped to an IP address (this is the job of Domain Name Server[DNS] to map the entered URL to particular IP address )

URI is basically a part of full URL, it points to specific address.

For Example: http://www.sun.com/aboutsun/index.jsp

So here /aboutsun/index.jsp wil be the URI. Pointing towards the specific address of index.jsp page.