For example, it might be available in different languages or different media types, or a combination. One way of selecting the most appropriate choice is to give the user an index page, and let them select. However it is often possible for the server to choose automatically. This works because browsers can send as part of each request information about what representations they prefer. For example, a browser could indicate that it would like to see information in French, if possible, else English will do.
Browsers indicate their preferences by headers in the request.
If a resource is available in several formats, these are called representations or variants . The ways in which the variants for a particular resource vary are called the dimensions of negotiation. In order to negotiate a resource, the server needs to be given information about each of the variants. See comments in the sample config files for details. Entries for different variants are separated by blank lines.