There are two basic types of presentations (or oral reports) that you will likely be called upon to deliver during your educational career and beyond — informative presentations and persuasive presentations.
The purpose of an informative presentation is to promote understanding of an idea or to convey information. They are often used to provide people with information about a concept or idea that is new. A presentation on "Endangered Species in the South American Rain Forest" is an example of an informative presentation.
The second type of presentation is a persuasive presentation. The goal of a persuasive presentation is to influence a change in the belief, attitude, or behavior of another person when that person has some degree of free choice. Expanding upon the example provided above, a persuasive presentation would not only inform the audience members about the South American rain forest and its endangered species, but would also try to get them to take specific and appropriate action to save these species.
Both types of presentations can be used to start a discussion by providing information on a given topic followed by time for questions, answers, and discussion.