Letters that are Person-to-Person
A letter from one person to another are defined as person-to-person letters. These typically deal with personal matters. They can be written as formally or informally as the writer choses.
Letters that are Person-to-Business
A letter from a person to a company of organization of some sort and relates to business in some way is a person-to-business letter. The writer should keep to a formal style.
Letters that are Business-to-Business
A letter from a business party to another business party is considered a busines-to-business letter. These do encompass letters within a company.
"Business" can be used to include any type of organization intent on a product or service, either for-profit or not-for-proft.
Letters that are Business-to-Person Letters
A letter from a business to a person, to potentially include a customer, is a business-to-person letter. The topic of this type of letter must be about the business between the writer and the reader."Business" can be used to include any type of organization intent on a product or service, either for-profit or not-for-proft.