meta
Meta is a part of x-metadata and provides specific information about the book itself. In case of using Microsoft Reader, x-metadata can contains <meta name="ms-chaptertour"..> tag

Example: 

<metadata>
 <x-metadata>
  <meta name="ms-chaptertour" content="chaptertour"/>
 </x-metadata>
</metadata>

attributes

id
Provides an element with a unique name within a single document. This is especially useful in works with extensive cross-referencing and linking, such as dictionaries, encyclopedias, or travel guides. Use of ids  simplifies linking and updates.
class
Affiliates an element with one or more classes.
name
Name of meta
content
Content of meta
scheme
Scheme

See also:

<x-metadata>