Data transformation is a systematic process of converting data from one format to another. It involves various activities such as converting data types, cleaning data by removing duplicates and null values, enriching data, and performing aggregations. The process of data transformation consists of four main steps: data discovery, data mapping, code generation, and code execution. There are two types of data transformation: batch data transformation and interactive data transformation. Data transformation is necessary when moving data to a new data store, integrating data from different systems, joining structured and unstructured data, enriching data, or performing aggregations. The benefits of data transformation include higher data quality, reduced errors, improved query time, minimal resource usage, and better organization of data.