An informal essay can refer to a number of different things, depending on the level of education a student has reached, and the type of course he or she is in, as well as the overall purpose of the assignment. In general, this type of essay is written as a reflection or a response to something, or is written as a type of informational piece about a personal experience. This type of essay may also be written as fiction. These are just a few of the many options for informal writing; an instructor will provide specific directions as to the focus and length of the essay.
A common misconception when students are assigned an informal essay is that important rules of spelling and grammar go out the window. It is still important to use proper, formal language when writing informally in an educational setting, unless the piece is fiction and the language is deliberate. The length of this type of essay can vary, but generally it is fairly short as compared to more in-depth pieces, such as research papers. It is still important to have a clear focus in any essay, and a cohesive idea of what the essay is about.
A reflective essay is one of the most common types of informal essays. These are often written in response to a certain experience, such as watching a film, reading a book, or taking a class. Students who participate in community events or volunteer days are often asked to write an informal essay about the experience as well. In addition, if a student attends an event for extra credit -- such as a lecture or a play, for example -- the instructor might require an informal essay in order to get the extra credit to ensure the student actually went to the event.
Many students will also assign compositions to students simply to test writing skills and to determine how much the students have learned. This is especially common in the younger grades when students are still learning basic writing skills. A teacher will often provide a simple prompt and encourage students to write an informal essay about it. Students might be prompted to write a fictional story, or they might be asked to tell a story about an experience they have had. Asking students to summarize what they have learned that day in school is another common essay writing prompt.