Pages and entries are technically very similar to one another. In fact most, if not all, of the <mt:Entry*> tags will work for publishing pages and vice versa. Therefore, to more clearly differentiate within templates between pages and entries the <mt:EntryClass> tag returns one of two values: "page" or "entry" depending upon the current context you are in.

Example:

    <mt:If tag="EntryClass" eq="page">
        (we're publishing a page)
    <mt:Else>
        (we're publishing something else -- probably an entry)
    </mt:If>