It is, broadly speaking, an intermediary between a buyer and a seller. It is a term widely used in the stock markets, Forex and Real Estate, but it can also be applied to travel agencies, talent agents, bookmakers, among many other means.
They have been around for a long time and have the enormous advantage of having enough means to move resources from point A to point B quickly and safely.
Why use a broker as a buyer?
Because many times we want to invest our money or exchange it, but sometimes we have the insecurity of knowing that our money will be backed. With a well-established broker you can make investments with security and confidence, something very important to guard against scammers.
Why use a broker as a seller?
Because these institutions over the years have cultivated a portfolio of reliable clients, in addition to supporting your money or service, the other side of the coin.
A reliable broker is honest with both parties and supports all their movements, in addition to having responsibilities with the government of their country, it is not like any seller or promoter of any services, it is really an institution.