The trend is the general direction in which your weight is moving as opposed to your actual day-to-day weight which fluctuates.  The "trend line" is the green line on your weight graph.  Think of it as your true progress.   When your trend line goes down,  you are going forward to lose weight; when your trend line is flat, you have reached a plateau; when your trend line goes up, you are gaining weight even if your weight goes down on a particular day. To show a trend, you have to log your weight frequently, but never more than once a day.