What are courier services?

Give the name of any two courier companies and discuss their functioning too.

Courier service is provided by the individual post office. These are the private one which serve as the good alternative to the government run post offices. First Flight Couriers Limited and Blue Dart are the two examples of courier companies.
Their functions are
(i) These companies perform a very important function of delivering documents, gifts, etc from
one place to other.
(ii) These companies facilitate mail services with hundred percent of efficiency.
(iii) These allow speedy transmission of articles, documents, gifts, goods, etc to people in specified cities.