An intermediary (or go-between) is a third party that offers intermediation services between two trading parties.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.he 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.