What other thing would you guess this program might have. How about functions. Yep, and they had to call them methods just to confuse us. It also has many variables and functions that operate behind the scenes that we can't get to. We can only access certain properties of an object and use certain methods.
Objects can contain other objects.
A window contains documents with the document being your actual web page. Documents contain images, forms, tables, links, and etc. All of these items are objects of the document. The object contained by another object is a property of that object. Remember that we learned that variables, i.e. properties in this case, can have a value of the object type.