Grievous Bodily Harm refers to injuries that are more serious than others.  Broken limbs, fractured skulls and, in extreme circumstances, psychiatric conditions are all examples of injuries that will result in charge for GBH.

S.18 Offences Against the Person Act 1861 

A person may be charged GBH if they intentionally cause an injury of the seriousness described above. 

S.20 Offences Against the Person Act 

A person may be charged with GBH if they cause the injuries described above even if they do not intend to bring about that level of harm.