Introduction: The first paragraph of your essay. It is the first impression your readers recieve, and explain the main point of your paper. Your introduction contains your thesis statement.
Body: The paragraphs in between your introduction and conclusion. The body of your paper supports the main point of your paper.
Topic Sentence: The sentence at the beginning of each body paragraph. It explains the main point that paragraph is going to make.
Conclusion: The last paragraph of your paper. It closes the paper and leaves the reader satisfied with what they just read. Summarizes your paper in an effective way.
Source: http://www.unc.edu/depts/wcweb/handouts/introductions.html (7/20/2010)
Source: http://facweb.furman.edu/~moakes/Powerwrite/body.htm (7/20/2010)
Source: http://www.unc.edu/depts/wcweb/handouts/conclusions.html (7/20/2010)