How it works
The results are displayed as latitude and longitude, and UTM coordinates.
The accuracy is an estimate of how close to those coordinates you actually are. The accuracy value returned is intended to correspond to a 95% confidence level (the device's actual position is within the displayed number of meters of the position given 95% of the time).
Experiments have shown that when an accuracy is quite low, hitting "reload" to re-calculate sometimes results in a more accurate location. This could be because the phone's GPS unit requires some time to get a fix, or the device's cellular signal strength changed.