An empty element has no content, only attributes. Its format is:
<tag attribute1="value1".../>
Where values are strings.
The format of a non-empty element is:
<tag attribute1="value1"...> content </tag>
Where content can be a mixture of other HTML elements depending on the tag. This means we can view the structure of an HTML document as a tree, where elements are nodes, and element A is a child of element B if A occurs in the content of B.
The root of the tree is the html element:
<html>
<head>
meta data goes here
</head>
<body>
body elements go here
</body>
</html>