What is document.location?

[UniteMage]

What is document.location in the following code?

Application.ExternalEval(
    "if(document.location.host != 'unity3d.com') { document.location='http://unity3d.com'; }"
);

Thanks CSDG

[DaveA]

http://docstore.mik.ua/orelly/web/jscript/refp_88.html