Question

what are the things different between formal and informal letter

Answer 1

Formal letters are letters which we write to head of a company or school like principal or shop manager
Informal letters are those of which we write to our family members or friends.
Hope it helps! Thank you!

Answer 2

formal letters include business or commercial letters, official letters ( letters of application),and social letters (notes of invitation)

informal letters include friendly or private letters written to family , friends or person of close acquaintance.