Due to incompatibility between Scala versions, there are several scala-x modules for each supported Scala version. Due to incompatibility between Spark versions, there are several spark-shims modules for each supported Spark version.
spark-scala-parent- Parent module for each Scala module
scala-2.11- Scala module for Scala 2.11
scala-2.12- Scala module for Scala 2.12
scala-2.13- Scala module for Scala 2.13
spark-shims- Parent module for each Spark module
spark2-shimsspark3-shims