The crosshair in MetaTrader is a great tool that makes the life of traders much easier. Simply click on your mouse wheel or use the MetaTrader hotkey CTRL + F and you will see the crosshair in the price chart.
When you click and hold your right mouse button, you can then activate the measurement feature of the MetaTrader crosshair. Move your cursor around and MetaTrader will show you the distance between the price level where you first clicked and your current cursor position.
The crosshair function is ideal to measure potential stop loss/take profit distances, explore chart pattern targets or measure other price distances.
MetaTrader will show you three numbers next to your cursor:
1) The amount of periods between your current mouse position and the start
2) The amount of pips between your current mouse position and the start
3) The current price level