Spark SQL is a module in Apache Spark that provides a programming interface for working with structured data using SQL (Structured Query Language) and a DataFrame API for programmatically manipulating data. Spark SQL allows you to seamlessly mix SQL queries with Spark programs, providing a powerful tool for data exploration and analysis.

Some of the key features of Spark SQL include:

• Support for a wide variety of data sources, including Hive, Avro, Parquet, ORC, JSON, and JDBC
• Ability to perform SQL queries on data stored in HDFS, HBase, and other data sources
• Support for UDFs (user-defined functions) and UDAFs (user-defined aggregate functions)
• Integration with other Spark modules, such as Spark Streaming and MLlib