A courier is employed to deliver messages, packages and mail. Couriers differ from ordinary mail services by speed, security, tracking, signature, specialization and individualization of services, and committed delivery times

Couriers are usually more expensive than usual mail services, and their use is typically restricted to packages where one or more of these features are considered important enough to warrant the cost.

Different courier services operate on all scales, from within specific towns or cities, to regional, national and global services. The world’s largest courier companies are Aramex, DHL, FedEx, TNT N.V. and UPS.[