The <div> and <span> elements, in conjunction with the id and class attributes, offer a generic mechanism for adding structure to documents. These elements define content to be inline ( <span> ) or block-level ( <div> ) but impose no other presentational idioms on the content. Thus, authors may use these elements in conjunction with style sheets, the lang attribute, etc., to tailor html to their own needs and tastes.
Suppose, for example, that we wanted to generate an html document based on a database of client information. Since html does not include elements that identify objects such as "client", "telephone number", "email address", etc., we use
and to achieve the desired structural and presentational effects.