uni
Each information resource on the web has an address which can be codified by a URI (Uniform Reource Identifier).
<scheme>:<scheme-specific-part>Scheme is the name of the mechanism used to access the resource (eg. HTTP protocol)
URL
A uniform resource locator (URL for short) is a URI that:
- identifies a resource
- specifies the means of acting upon and obtaining the representation for the resource
URN
A uniform resource name is a URI that identifies a resource by name, in a particular namespace.