Difference between writing a personal letter and writing a business letter?

Personal letters differ from business letters in the tone and content. Personal letters are very informal in the use of grammar and vocabulary. It is written in a personal style. There are no specifications for the content or a personal letter, any topic of interest to you and your recipient is acceptable and any amount of details or anecdotes can be used.

Business letters needs to be written with higher standards, a more formal grammatical structure, and standardized vocabulary in a professional tone. The content should be focused on the outcome desired, the purpose of the letter, with enough information to achieve that goal without going off target. A business letter should be concise, to the point.