Worldwide computing is an emerging discipline with the goal of turning the Internet into a unified distributed computing infrastructure. Worldwide computing tries to harness underutilized resources in the Internet by providing various Internet users a unified interface that allows them to distribute their computation in a global fashion without having to worry about where resources are located and what platforms are being used. Worldwide computing is based on the actor model of concurrent computation and implements several strategies for distributed computation such as universal naming, message passing, and migration. This section introduces the worldwide computing model and how it is supported by SALSA.