This document introduces Orleans, a .NET framework for building scalable and distributed applications. Orleans uses an "actor model" where application logic is encapsulated in virtual actors that process messages asynchronously. The document defines Orleans terminology like grains, silos, and clusters. It also provides examples of how to structure grains and discusses use cases like stateless workers. Potential scaling issues are noted, such as the need to shard data storage and restart the cluster to redistribute grains at high load.