Market makers use inside knowledge, experience, and technology to make profits on a daily basis. They take profits on the stocks they make a market in, but they also take speculative positions on the possibility of future price movements of those stocks – depending on the time of day, the market conditions, and the existing order flow.
The major responsibilities of market makers include the filling of orders on behalf of the customer.
They also fill orders for their own account. Market makers also benefit from the difference between the ask and the bid prices, in terms of acting as a dealer.
Market makers are required to post a price at which they are willing and able to buy and sell.