Informative essays are actually the same as expository essays. The main difference in nomenclature is that "informative essay" describes what the essay does (it informs) while "expository essay" describes how it is done (though expounding). When informative essays are written for public audiences, they may be informal and use anecdotes and personal pronouns. However in academic settings, informative essays are formal and written in academic style that presents information and arguments objectively and that is without contractions, colloquialism, or personalization (except where instructor preference requires otherwise).
Informative essays provide information in one of a number of organizational patterns. Some common patterns for informative essays are cause and effect, definition, sequence of steps or events, comparison and contrast, descriptive, and problem and solution. Often used in academic writing, some of these informative essay patterns are required in technical writing classes, such as sequence of steps essays that act as manuals for how to do something. Informative compare and contrast essays are frequently required in literature classes for comparing such literary elements as theme or character.
Informative essays, like all expository essays, are structured with an Introduction, argument paragraphs, counter-argument paragraph, Conclusion. The Introduction includes an arguable thesis statement (or question). "Arguable" means your thesis will engender disagreement or countering assertions. Your argument paragraphs will present well founded information derived from expert opinion; your own analysis; field study surveys, interviews or other data; statistics; and other academically sound research material. In addition, in each argument paragraph (one supporting argument per paragraph) you will evaluate the argument and show its relationship to your thesis.
After objectively presenting your own arguments in support of your thesis, you will then objectively present one (or two) countering arguments (the other side), with an evaluation and statement of its relationship, either supporting or contradicting, to your thesis.
Your Conclusion will reiterate your thesis argument while indicating how you've achieved its successful proof. You may also make a statement about the relevance of your topic and thesis to present or future application or study. Your Conclusion will be about as long as your Introduction so succinct language and concise statements are required.