Google App Engine lets you run web applications on Google's infrastructure. App Engine applications are easy to build, easy to maintain, and easy to scale as your traffic and data storage needs grow. With App Engine, there are no servers to maintain: You just upload your application, and it's ready to serve your users.
You can serve your app from your own domain name (such as http://www.example.com/) using Google Apps. Or, you can serve your app using a free name on the appspot.com domain. You can share your application with the world, or limit access to members of your organization.
With App Engine, you only pay for what you use. There are no set-up costs and no recurring fees. The resources your application uses, such as storage and bandwidth, are measured by the gigabyte, and billed at competitive rates. You control the maximum amounts of resources your app can consume, so it always stays within your budget.
App Engine costs nothing to get started. All applications can use up to 1 GB of storage and enough CPU and bandwidth to support an efficient app serving around 5 million page views a month, absolutely free. When you enable billing for your application, your free limits are raised, and you only pay for resources you use above the free levels.
The Application Environment
Google App Engine makes it easy to build an application that runs reliably, even under heavy load and with large amounts of data. App Engine includes the following features:
dynamic web serving, with full support for common web technologies
persistent storage with queries, sorting and transactions
automatic scaling and load balancing
APIs for authenticating users and sending email using Google Accounts
a fully featured local development environment that simulates Google App Engine on your computer
task queues for performing work outside of the scope of a web request
scheduled tasks for triggering events at specified times and regular intervals
Your application can run in one of three runtime environments: the Go environment, the Java environment, and the Python environment, which gives you a choice of Python 2.5 or the experimental Python 2.7. Each environment provides standard protocols and common technologies for web application development.