What is the difference between formal and informal essays?

The informal essay is written mainly for enjoyment. This is not to say that it cannot be informative or persuasive; however, it is less a formal statement than a relaxed expression of opinion, observation, humor or pleasure. A good informal essay has a relaxed style but retains a strong structure, though that structure may be less rigid than in a formal paper. The informal essay tends to be more personal than the formal, even though both may express subjective opinions. In a formal essay the writer is a silent presence behind the Words, while in an informal essay the writer is speaking directly to the reader in a conversational style. If you are writing informally, try to maintain a sense of your own personality. Formal essay's also fallow a very rigid structure with proper and technical grammar and vocabulary.

formal is when you are very polite and well manered, and informal is the opposite.