The Document Root identifies the location from where the Web server will serve content to the browser. Content resources for a domain are located in the document root of the subdomain. For example, if your domain files are placed in the document root - /usr/web, then a request for http://www.sales.abc1.com/index.html will actually be sourced from the path - /usr/web/index.html
The base of a Web server's document tree, the root defines the scope of all the documents that Web users may access (i.e., access is allowed to the root and all its children, but not to any of the root's peers or parents).
The base of a HTTP server's document tree.