"Market Makers" are brokers who play the role of your counterparty for each forex trade you make. If you buy EUR/USD they sell it to you and vice versa.
In this sense you have opposite interest than your broker or usually it is stated that there is a conflict of interest between you and the broker.
The exchange rates that market makers set, are based on their own best interests. As counterparties, many of them will then try to hedge, or cover, your order by passing it on to someone else. There are also times in which market makers may decide to hold your order and trade against you.
It is a widely spread misunderstanding that all client losses go directly into brokers pocket. The broker rather takes all its clients position and form a single net position which is then taken in or out of the pocket or hedged with other counterparty.
If you think for a minute, you will find out that you are also a market maker because the position you open is at your own risk and you can take it in or out your pocket or decide to hedge it with another broker. There is no difference in how you and your broker manage the risk.