A uniform resource locator, abbreviated URL, also known as web address, is a specific character string that constitutes a reference to a resource. In most web browsers, the URL of a web page is displayed on top inside an address bar. An example of a typical URL would be"http://en.example.org/wiki/Main_Page". A URL is technically a type of uniform resource identifier (URI), but in many technical documents and verbal discussions, URL is often used as a synonym for URI, and this is not considered a problem.
A URL is a URI that, in addition to identifying a web resource, provides a means of locating the resource by describing its "primary access mechanism (e.g., its network location)".
On the Internet, a hostname is a domain name assigned to a host computer. This is usually a combination of the host's local name with its parent domain's name. For example, en.example.org consists of a local hostname (en) and the domain name example.org. The hostname is translated into an IP address via the local hosts file, or the domain name system (DNS) resolver. It is possible for a single host computer to have several hostnames; but generally the operating system of the host prefers to have one hostname that the host uses for itself.
Any domain name can also be a hostname, as long as the restrictions mentioned below are followed. For example, both "en.example.org" and "example.org" can be hostnames if they both haveIP addresses assigned to them. The domain name "xyz.example.org" may not be a hostname if it does not have an IP address, but "aa.xyz.example.org" may still be a hostname. All hostnames are domain names, but not all domain names are hostnames.
