Expected goals, or xG, estimates how likely a shot is to become a goal. A tap-in from a few metres might be worth around 0.8 xG, while a long-range effort may be worth under 0.05.
How it is built
Models learn from large numbers of past shots. Typical inputs are distance, angle to goal, whether it was a header or a foot shot, and the type of pass that created the chance.
How to use it
Add up every shot's xG and you get a sense of the chances a team created. If a side wins 1-0 but its xG was far lower than its opponent's, it may have been fortunate.
xG has limits. It says little about goalkeeper quality or finishing skill, and different providers use different models, so compare numbers from one source only.