Difference between URL,URN,URI.
URL
The idea is that a URL is a mechanical link to a resource's location, where it can be downloaded. For this reason, a URL contains a hostname and a local part, all of which can be resolved anywhere on the Internet.URL
A URL is a specialization of URI that defines the network location of a specific resource. Unlike a URN, the URL defines how the resource can be obtained. We use URLs every day in the form of http://damnhandy.com, etc. But a URL doesn’t have to be an HTTP URL, it can be ftp://damnhandy.com, smb://damnhandy.com, etc.
URI
A URI identifies a resource either by location, or a name, or both. More often than not, most of us use URIs that defines a location to a resource. The fact that a URI can identify a resources by both name and location has lead to a lot of the confusion in my opionion. A URI has two specializations known as URL and URN.
URN
What a URN tries to do is different. It tries to give a description of a resource without actually pointing at it. For example:urn:isbn:90-365-17273
A URI identifies a resource by name in a given namespace but not define how the resource maybe obtained. This type of URI is called a URN.
URI is merely the possibly overlapping union of strings that are a URL or a URN