A Linked Data page is a web page that explicitly describes one or more things (objects) via hyperdata links. Unlike traditional web page hypertext links, hyperdata links expose properties (attributes or relationships) and property values associated with the things in a page. Linked Data pages can be created by hand or generated dynamically (via a linked data server or user agent).
You only need a single reference (a URI or IRI) to a thing to experience the power of serendipitous data discovery offered by a Linked Data page.
How is this different from a basic web page?
A typical web page is not endowed with links that explicitly describe anything. Its links simply expose unqualified associations with other documents on the Web.
Put differently, Linked Data pages reveal explicit properties of "things" while basic web pages are loosely "about anything", requiring human interpretation and reasoning in order to attain clarity.