The CAMS Global Reanalysis contains a parameter (variable) called  'GEMS Total column ozone' and a parameter called 'Total column ozone'. What is the difference between the two?

Moreover, some CAMS Global datasets have two parameters (variables) called 'GEMS Ozone' and 'GEMS Total column ozone'. What is 'GEMS' in this context?

Is 'GEMS Ozone' different from the 'Ozone' in other ECMWF-produced data?