Expected Goals (xG)
Meaning
Number of goals that would be expected from an average player/team
Calculation
The probability of a goal being scored is determined for each throw using the location, type of throw and other variables. These values can be added up over one or more games and compared with the number of goals actually scored.
Some models are very simple and use just the raw shooting area more advanced ones use more detailed data and machine learning approaches.
Interpretation
More meaningful shooting statistic than just the number of shots (on target).
Can for example show whether a player/team scores better or worse than an average player/team would (also called xG Efficiency) or the quality of the scoring positions of players/teams (also called Shot Quality).
In football, Expected Goals have shown to allow better predictions than actual results because of the high role chance plays in football due to the few goals. In handball, chance plays a clearly lower rules and similar analyses have not been made yet.