AWS Step Functions is a cloud workflow engine that helps developers orchestrate multiple serverless functions, such as AWS Lambda, without relying on the application itself to perform coordination work. It allows designers to create visual workflows, or "state machines," that coordinate the order and conditions in which serverless functions should be called. The technology provides an integrated environment primarily designed to ease the orchestration of AWS Lambda functions, making it a valuable tool for building cloud-native apps that interact with multiple systems. A good use case for Step Functions is demonstrated through a sample app that integrates MongoDB Atlas, Twilio, and AWS Simple Email Service to notify users about possible restaurant matches in their area. The author built three AWS Lambda functions to achieve this: GetRestaurants, SendBySMS, and SendByEmail, showcasing the flexibility of Step Functions' inputs and outputs.