What is a "courier market",a post service, a tourism market, or a delivery market?

A courier is a person (or a business) which contracts to carry goods from one place to another for people. In a sense, the postal service is a courier service, though the word usually applies to services which are different from the normal mail - they are either more secure or faster or can carry items which could not be sent by mail. The "courier market" refers to the section of business where, in particular, courier services are bought and sold - the market for courier services. The term "market" is often used like this to mean a particular area of business, for example, 'the landscape gardening market' or 'the education market'. It is economic jargon (= a specialised term used by economists) and means a virtual group of things, rather than a physical location. It is often used in phrases like: "The XXX market [or 'the market for XXX'] is rising/falling/decining/strong/weak." "It is difficult for small businesses to break into the footwear market, due to the preponderance of large chains." (= "Small businesses selling shoes find it very difficult to compete with the many large and well-established ones who own shops in many towns and cities.")