A broker is a neutral and trusted person or an institution (such as a consulting firm) involved in an agreement who serves as an agent or intermediary between two or more parties such as between a buyer and seller to achieve successful bargaining and transactions. They are needed to provide professional advice to people and companies who are about to engage in a business transaction or are already in the process. Such professional/expert advice covers several areas like Valuation/financials, corporate governance, due diligence, investments, procurement, legal, strategy, real estate, etc.
A fee called brokerage commission is usually paid to a broker for rendering his/her services. A broker is advised to be consulted especially when you have little or no knowledge about the transactions you are about to make in order to prevent wastage of resources and future regrets.