There are many types of essay because there are many different points to get across within your work. There are also some types of essay that are more suited to some types of essay than others are. Essay types or not as structured or strict as essay structure, but if you defy convention too much then your college or university will probably mark your work lower. They will probably assume you do not understand how to write a certain type of essay. Here is just a small selection of very popular essay types.
This is where one idea is compared to another in an argumentative fashion. You may write it as an argument and counter argument that leads to a conclusion, or you may write numerous arguments for the first half and write numerous counter arguments in the second half. The amount you write per argument or counter-argument is of no concern. Your aim is to keep it as unbiased as possible, and that is possible even if the text appears weighted (i.e. there is more) on one side rather than the other.
This is where you describe something in detail. You introduce the reader to it and help them understand what it is you are describing, and you then describe it in as much detail as needed. It is very similar to an expository essay, where an expository essay is caught between a description essay and a definition essay. With an expository essay, you may be more easily forgiven for giving your opinions and evaluations as evidence (hopefully logic based evidence). A description essay is a little more matter-of-fact.
This is where you nail the definition of something. You explore an idea, word, object, place, etc, and you open it up so that any realistic questions about its meaning are answered.
These exist to help students practice their essay writing skills and shows them that they can get a point across without resorting to thousands of words. It is also a very good format for essay competitions or for subjects that do not require a large amount of work dedicated to them. Many students find them difficult because they are quite restrictive when it comes to word count and structure in general.
This may be set out like an argumentative essay, but its aim is not to be unbiased. You may put forward a better argument if you can show that you are unbiased, but that is not the point of the essay, the point of the essay is to set a persuasive goal and achieve it by the end of the essay. Ideally, the reader should have no counter questions or counter arguments by the time the conclusion is reached.
This essay allows you to give your interpretation of something. Your interpretations should ideally be based on evidence, current theory (or your theory), your current learning and what is considered to be logical. Like most essay types, it is very easy to get this very wrong, but you may not lose as many marks if you can justify why you came to your interpretation and subsequent conclusion.