The Page you are viewing right now is an HTML document. You can have bold and italicized , Larger and Smaller , or it could look type-written . When you place a certain thing within these you are making something known as a tag. Many opening tags require a following closing tag, but not all do.
Tags make up the entire structure of an HTML document.
Tags in HTML are NOT case sensitive. The body is the larger part of the document, as the body of a letter you would write to a friend would be. The head of the document contains the document's title and similar information, and the body contains most everything else. Whatever you place between the BODY tags will fall into the major area of the document window, and therefore it is the largest part of your HTML document.