In diplomacy and international relations, an intermediary may convey messages between principals in a dispute, allowing the avoidance of direct principal-to-principal contact.  Where the two parties are geographically distant, the process may be termed shuttle diplomacy.
The intermediary acts as a conduit for goods or services offered by a supplier to a consumer. Typically the intermediary offers some added value to the transaction that may not be possible by direct trading.
Common usage includes the insurance, and financial services industry where e.g. mortgage brokers, insurance broker, and financial advisers offer intermediation services in the supply of financial products such as mortgage loans, insurance, and investment products.
In barter, the intermediary is a person or group who stores valuables in trade until they are needed, parties to the barter or others have space available to take delivery of them and store them, or until other conditions are met. In a larger sense, an intermediary can be a person or organization who or which facilitates a contract between two other parties.
The Internet is creating a transparent awareness on the threats and opportunities available to automate intermediaries in many industries.
Intermediaries can be classified as merchant intermediaries or as accountant intermediaries. Bailey and Bakos (1997) analyzed a number of case studies and identified four roles of electronic intermediaries including information aggregating, providing trust, facilitating and matching.