From OpenStreetMap Wiki
|building = cathedral|
|A building that was built as a cathedral.|
|Used on these elements|
|Status: in use|
|Tools for this tag|
Aon Wikipedia is a Christian church which contains the seat of a bishop.
There are other churches as well, which were built with the same architectural features, but they do not have or never had a bishop, but they are called cathedrals as well.