Churning is the name for the practice by unscrupulous stockbrokers who make excessive trades of stocks on behalf of their clients not to maximize the profit of their clients, but to maximize their own fees for making the trades since the stockbroker gets paid every time he or she makes a trade.
It rarely makes sense to give your stockbroker the authority to trade whenever he or she wants. Make sure that you make the final decision on any recommended trade. And read your monthly statement. Many people fail to do so because the monthly statements appear to be too confusing.