What is the difference between varname and hivename in MetastoreConf.java?

What is the difference between varname and hivename in the picture below?

How is the Hive MetaStore authenticated for accessing HDFS?

Hey, How is the Hive MetaStore authenticated for accessing HDFS? Will it be automatically re-certified when the certification expires? Is it related to hive.metastore.kerberos.key.file and hive.metastore.kerberos.principal? Thank you