What is a ground fault?
A short circuit means the circuit is shorted so too much current flows. More current than the wires and switches etc. can handle. If that current continues to flow, there is a risk of overheating and fire.

Read here about Ground Fault Protection.

The ground is there to protect people from electric shock. Your washing machine doesn't care if its metal case has an AC voltage of 120 or 240 V relative to ground. It will still work! But if you touch it then you would get an electric shock. That we want to prevent and that is why grounding is needed. The metal case of your washing machine should be grounded, so connected to ground. That ground is often a metal pin that literally sticks into the earth. It must not have any voltage on it so that it is safe to touch.

Now if your washing machine develops a fault and it makes a connection between the mains and ground then current "escapes" via the ground. The Ground Fault Protection detects that and switches everything off for your safety.

The circuit breakers that protect against short circuits and grounding faults just combine the two functions in one device. You should always have both protections installed in any installation for added safety. It does not matter if short circuit protection and ground fault protection are in one device or separate devices connected in series.