Explanation:

An intermediary (or go-between) is a third party that offers intermediation services between two parties, which involves conveying messages between principals in a dispute, preventing direct contact and potential escalation of the issue. In law, intermediaries can facilitate communication between a vulnerable witness, defendant and court personnel to acquire valuable evidence. Whilst 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.
An 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 relation to energy supplies, third party intermediaries provide energy-related advice, assistance in purchasing energy and management of energy needs.