The calculator works out where to put a stop-loss and take-profit in order to achieve a cash result.
You define the target/risk either as a fixed cash amount, such as $100, or as a percentage of an equity figure. You also need to choose the market you are trading, and the volume (as either a number of lots, or a notional amount such as 100,000).
The calculator will then work out the distance to the stop-loss and take-profit in order to achieve the specified cash risk/target, e.g. a distance of 0.0010/10 pips in order to achieve $100 when trading 1 lot of EUR/USD on a USD account.
If you also enter a trade direction and an open price, the calculator will tell you the corresponding stop-loss and take-profit prices as well as the offset.