Apache Tez is a customizable orchestration framework for data processing applications on YARN, designed to operate efficiently in a distributed Hadoop environment. It features a flexible Directed Acyclic Graph (DAG) definition that enhances performance, enables fault tolerance, and utilizes shared components across various processing models like Hive and Pig. Tez's integration into these systems provides substantial performance improvements and supports large-scale analytics, making it a foundation for modern data processing workloads.