India has 29 states with at least 720 districts comprising of approximately 6 lakh villages, and over 8200 cities and towns. Indian postal department has allotted a unique postal code of pin code to each district/village/town/city to ensure quick delivery of postal services.
A Postal Index Number or PIN or PIN code is a code in the post office numbering or post code system used by India Post, the Indian postal administration. The code is six digits long. You can find out the pin code of state Bihar right here.
The first three digits of the PIN represent a specific geographical region called a sorting district that is headquartered at the main post office of the largest city and is known as the sorting office. A state may have one or more sorting districts depending on the volumes of mail handled. The fourth digit represents the route on which a delivery office is located in the sorting district. The last two digits represent the delivery office within the sorting district starting from 01 which would be the GPO or HO.