Informal and formal essays differ in terms of context and style. During your educational career, you will craft mainly formal essays, which are research-based, factual and written in the third-person point of view. In contrast, informal essays, also known as personal essays, can be written in the first-person voice and tend to be subjective and opinion based.

Writing an Informal Essay

Use a relaxed and casual tone for informal essays. Unlike formal essays, which are often divided into sections and written in a specific writing style, an informal essay should reflect your opinion and sound like your voice. In an informal essay, use the pronouns "I" and "me." A passage in an informal essay may read: "I spent the last year traveling through Asia. I am sharing my story in hopes that it encourages others to go on adventures and explore the world." Though not common academically, informal essays are ideal for personal letters, blog posts and magazine or newspaper editorials.

Writing a Formal Essay

A formal essay is heavily structured; it includes cited research, has a clear introduction, body and conclusion and supports a stated thesis. This type of essay also employs a formal tone -- it is written in third-person. This is the type of essay you will be expected to write in an academic setting. For example, if you are writing an essay about the theory of evolution, introduce the topic broadly in the introduction, go into detail about the theory based on your research in the body paragraphs and then summarize your findings in the conclusion. Even if the essay you are writing is a persuasive piece -- one in which you try to convince the reader of your stance on an issue -- you still have to back up your arguments with researched facts.