what do we call informal and formal letters in hindi????????

  aap ek chatravas(hostel) mein rahte hai , kuch pathye pustak kharidne ke liye aapko paiso ki avaśyakata hai.  paise mangvate hua apne pita ji ko ek patra likhiye.

i want a letter in hindi to my grandmother

give the example of vigyapan

 i want a letter on mere jeevan ka lakshya

whats prativedan .fast tmrw is my SA1'

i want a letter in hindi to my parents 4 permission of a trip 4rm a hostel  

 an example of formal & informal letter should be provided for better understanding..

 write a letter to your friend describing your first day experince in your new class

write a letter to your small brother for not to cheat in exam.

kya nagarpalika aur nagar nigam ka patra ek jaisa hota hai.