Audience and Voice
Noun: the people who see the work of a particular artist or read the work of a particular writer1
When writing, it is very important to use language that fits your audience and matches your purpose. Inappropriate language uses can damage your credibility, undermine your argument, or alienate your audience. Some of the major issues with appropriate language use:
The flip side of the idea of audience is that of voice (sometimes called tone, mood or style). Every writer has their own unique voice and the use of that voice is what makes their writing unique. It is important that the writer's thoughts and ideas clearly show through their use of language - their voice. The writer's voice comes from the choices made while writing: the words, the organization, which details to include and so on. All of the choices the writer makes reflect that writer's voice.
It is often important that the writer's voice is not buried within a research laden paper.
NOTE: Do not confuse this with the grammatical subjects of Passive vs. Active Voice. You can find clarification on that subject at http://owl.english.purdue.edu/owl/resource/539/01/
2This section can be found at http://owl.english.purdue.edu/owl/resource/608/1/