With Hypertext and HTTP, URL is one of the key concepts of the Web. It is the mechanism used by browsers to retrieve any published resource on the web. URL stands for Uniform Resource Locator and is nothing more than the address of a given unique resource on the Web. In theory, each valid URL points to a unique resource. Such resources can be an HTML page, a CSS document, an image, etc. In practice, there are some exceptions, the most common being a URL pointing to a resource that no longer exists or that has moved.
As the resource represented by the URL and the URL itself are handled by the Web server, it is up to the owner of the web server to carefully manage that resource and its associated URL.
Uniform Resource Locator Definition
So how does your favorite browser navigate this tangled network of computers to find just the web page you want? It’s all in what is known as the URL (Uniform Resource Locator), which is simply the website address you type into your browser, like www.seotrance.com
The service or protocol part of the URL identifies the types of internet service the browser uses to access the resources
The host name is used to identify web resources on HTTP servers. Host names are optional.
The subdomain name identifies the name of the server hosting the resources
The Domain name identifies the type of entity providing the resource.
The Port number designates the specific TCP/IP port being used to process the request and will default to 80 if it is omitted.
The Directory identifies the location of the resources on the host server.
URL is the syntax and semantics for a compact string representation of a resource available via the Internet. For example, we use URL to locate web addresses and FTP site addresses. The generic syntax for URLs provides a framework for new schemes to be established using protocols other than those defined in this document. URLs are used to 'locate' resources, by providing an abstract identification of the resource location. Having located a resource, a system may perform a variety of operations on the resource, as might be characterized by such words as "access", "update", "replace", "find attributes". In general, only the "access" method needs to be specified for any URL scheme.