Answer:
Suitable examples include appreciation notes, letters of gratitude, recommendation letters, letters of favors, request letters and the likes. Personal correspondence may not have a strictly formal tone.
Business correspondence is a letter exchange between two businesses or organization for any business activities like a job application, complaint letter, etc. External, Routines, Sales, Personalized, and Circular are types of Business Correspondence.
Business letters are mediums used for communication between one or more companies, communication between employees in the company, or mediums used for different transactions you may want to make formally with different parties.