Pig is a framework for analyzing large datasets that sits on top of Hadoop. It allows users to write scripts for processing data in a simple query language called Pig Latin. Pig provides built-in functions and libraries for common tasks like joins, filters, and aggregations. It aims to make analyzing large datasets with MapReduce easier for users than writing Java code. The document then provides an example case study of using Pig to analyze Apache access logs and lists some resources for learning more about Pig.