It refers to Uniform Resource Locator – the naming style used for addressing online documents. The HTML page is the actual page on the domain and .html is its extension. The extensions .php, .xml, .gif, .jpg and others can be used to perform different functions.
The address can be opened by clicking on the link, or you can copy link URL and paste it in the browser address bar to view it. To protect users from phishing threat the automated detection systems should be integrated that helps to filter hazardous sites and it can also be used to remove dead URLs.