A rhetorical situation is one where you address an audience (be it written or spoken) with a purpose. Actually the rhetorical situation is not the act of addressing the audience but the combination and interaction of all the components you use to address the audience. You have a purpose, a known audience, a point you’re trying to get across, a genre that you’re speaking in, and a medium you’re speaking through. All are important elements that we, the writer, need to consider carefully.
Rhetorical situations don’t just come in a written form but apply to any situation where one person addresses another person or groups. A rhetorical situation could be the best man giving a speech at a wedding or a doctor addressing fellow physicians at a conference. For the purposes of this class we will view rhetorical situation in terms of writing but the elements are still the same and as stated in What Should I Know about Rhetorical Situations? a rhetorical or “writing situation” is one which “writers and readers bring different purposes, interests, beliefs, and backgrounds to the creation and reception of texts”
“Home.” The WAC Clearinghouse, wac.colostate.edu/resources/wac/intro/rhetoric/.