Documents or other items are often delivered from one place to another in a top-secret fashion, making the couriers who do these deliveries a rare, secretive group. Items are delivered for government or corporate purposes and are handled in a very circumspect manner, so that no one knows what exactly is being delivered or why it is being delivered except for the few people who are sending and receiving the package or information.
Diplomatic couriers work for the state departments of foreign nations and are trusted employees who deliver hard copies of documents, messages or contracts between diplomats from other countries all over the world. Some diplomatic couriers may operate within a city where there are a lot of foreign dignitaries living who must interact through agreements, contracts or other forms of formal communication. Others may travel the world to deliver top-secret documents to far off places. Or they live in a foreign country or city as a trusted employee of their government, delivering classified materials to the proper location so that the government can work effectively in those foreign locales.
Inner Government Courier
Many couriers work only within a particular government, passing messages, packages and documents between different agencies or departments of the government that cannot be sent in any other way for security reasons, or which need a particular signature on them. These couriers have high-level security clearances in most cases and have signed away their rights to disclose anything they see on the documents or packages they are delivering or the identity of the agencies or government offices from which they are receiving the documents and to which they are delivering them. This job is ideal for someone who has their own delivery service and vehicles for the delivery service, though they must also have clean personal and driving records before they are approved for the job's security clearance.
Private couriers can be hired to deliver documents or packages outside of the government so that only the people who have hired them and those they are delivering to know about the exchange. These couriers are often hired by major corporations who are doing business transactions together and trying to keep other major corporations or the general public from finding out about their dealings. International business is often conducted with the assistance of a private courier service, because they keep all their dealings t secret and between their clients. Many of these private courier services employ couriers who used to work for governments in some capacity.