In SAP FICO, Master data refer to those records based on which the various transactions takes place.
These Master data contains various information, details and controls by which the transaction has to behave.
FI consist of Master data like GL, Vendor, Customer, Asset, Bank and
CO has Cost Element, Cost Center, Profit Center, Activity Type etc.
In sap they have provided two parts
Master data is used by key user means it will enter day to day entries
Master data topics like this ie
excluded customization part remaining master data.