(a)description : expository writing is a type of writing where the purpose is to explain, inform or even describe.
(b)purpose : to explain and anylyze information by presenting an idea, relevant evidence, and appropriate discussion.
(c)examples : business letters, recipes and other instructions, news stories, personal letters, press releases, reports, scientific reports, term papers, textbooks, wills, encyclopedia articles, cuisines.
source of information : http://en.wikipedia.org/wiki/Rhetorical_modes
(a) How are expository texts different from narrative texts and personal recounts?
A narrative account is when you write about an experience or a story, when expository is factual and explains information.
source of information : http://answers.yahoo.com/question/index?qid=20100824163450AAgyOET