The essential PySpark module functions for data manipulation and processing include pyspark.sql for DataFrame and SQL operations, pyspark.sql.functions for built-in data transformation functions, pyspark.sql.types for defining column data types, and pyspark.ml for machine learning algorithms and tools.
If you have an interest in learning more about PySpark, I suggest exploring this comprehensive PySpark tutorial, which covers everything from the basics to advanced topics.