This tool is used to detect your current position on the map.
Click on the Location() tool. A red dot and a circle will be drawn on the map displaying you approximate location.
The circle represents radius in which you may be located. A numeric value of that radius will be written below the Location() tool.
You can also snap to this point when using Measure distance(), Measure area() or Editing() tool.
To deactivate the location mark click on the tool again.