Question

what is the difference between informal and formal letter?

Answer 1

in a informal letter you write your letter to you close relation or friends . in formal letter you write letters to someone superior to you like teacher,commisioner or some other officers.

Answer 2

Formal letters can be written to people of particular posts i.e someone superior who hold  any designation or post like Editor,Principal etc.Informal letters can be written to family(relatives),friends and dear ones.