To request for action or information. This allows one to have a written record of the request. As compared with an oral request, this type of written request is more difficult for the audience to...

To request for action or information. This allows one to have a written record of the request. As compared with an oral request, this type of written request is more difficult for the audience to forget or ignore.

To explain to the reader something that is not understood. The purpose in this case is to clarify something to the reader.