Pig is a dataflow language used for performing extract-transform-load (ETL) operations on Hadoop. It has a simple syntax called Pig Latin and translates scripts into MapReduce jobs. Pig was designed for data pipelines, research on raw data, and iterative data processing. It allows operations like joining, grouping, filtering datasets. Users can also define custom functions in Java. The document provides an overview of Pig and examples demonstrating how to load data, transform it using operations like filter and group, and define user-defined functions.