The Trade Manager is an expert advisor (EA) that allows you to plan your trade in terms of risk and profit targets, knowing the estimated profit and loss before entering the position.
The benefit of the trade manager is that rather than estimating where your stops and targets, or calculating them in your head or manually, you can actually see the automatic estimation based on the intended stop and target.
Put simply, you drag your stop level and target level to where you want it to be on the chart, and the trade manager shows you the anticipated dollar value of those levels.
This makes it easier to trade in line with your risk management policy and ensure your volume and stops are in the correct position BEFORE you enter the trade. Too many times, in the heat of trading do people enter a position thinking the stops are closer than they need to be, then moving them to the right position and amping up their risk beyond their original expectation. The Trade Manager allows you to map out the trade with your levels and understand the actual risk before hitting the button.
If you are serious about trading, and serious about risk management (the two go hand in hand), then you need the Trade Manager.