This document discusses using scikit-learn pipelines to build machine learning workflows in a modular way. It describes how pipelines can encapsulate data preparation steps as well as model training. The document then provides a case study example of building a pipeline to predict customer churn. Key steps include designing pipeline components to handle different data types, writing custom transformers when needed, and using grid search cross-validation to tune hyperparameters of estimators added to the end of the pipeline.