Google App Engine is a PaaS that allows developers to build and host web applications in the Google cloud. The document summarizes a workshop on using the Java runtime environment on GAE. It discusses the SDKs, deploying and managing apps on GAE, data storage using the datastore, and limitations like the 30-second request limit. The biggest benefits of GAE are scalability and low startup costs, while the hardest limit is the 30-second request processing time.