This is the 860th most frequent German word.
csu
The CSU (Christian Social Union) is a conservative political party in Germany, operating exclusively in Bavaria.
Here, 'CSU' is used as a proper noun referring to the Christian Social Union, a German political party.
Die CSU ist eine politische Partei in Bayern.
The CSU is a political party in Bavaria.
In this sentence, 'CSU' is used as a subject representing the political party that is associated with voter's choice.
Viele Menschen in Bayern wählen traditionell die CSU.
Many people in Bavaria traditionally vote for the CSU.
Here, 'CSU' represents the organization whose policies are being described.