I am new to Sitecore. Can any one please tell me why and how to use URL Rendering in Sitecore?
Welcome to Sitecore community. Url rendering is explained here .
This rendering type renders the response of a HTTP GET request onto the current page.
You can use it if you need to screen scrape HTML from another system. Can sometimes be used to avoid using iframes.
In Genreal, if you need to display any website in iframe in your website, you can use Url rendering.