Service - a collection of APIs, Events, Workflows, and Tasks that represent a business domain or capability. Can be composed with other services via APIs and Event subscriptions.
Command - create and your own APIs and serve them over HTTPS via a managed API Gateway.
Event - emit and subscribe Events to your Service's Event Bus. Process events internally or route them to other Services.
Workflow - a set of orchestrated Tasks that implements business logic with asynchronous, durable long-running processes.
Task - functions that encapsulate a single unit of work in a workflow. Integrate with cloud resources and SaaS.
Signal - a message that can be sent to a workflow execution. Workflows can wait for external input as a Signal and modify its behavior. Signals are communicated point-to-point in contrast to Events which are broadcast to all subscribers.