The purpose of an informative essay is to educate others on a certain topic. Typically, these essays will answer one of the five Ws: who, what, where, when, and why. Of course, they can also answer "how," indicating how to do something.
Informative essays must never express your opinion or try to convince others to take a certain action or stance. That role is expressly reserved for persuasive essays. Of course, if your informative essay is interesting enough, it may move readers to learn more about the subject, but they'll have to come to that on their own, thanks to the wealth of interesting information you present.
Read our examples of informative essays and learn more about choosing a topic and how to write an informative essay to help you get started.