The Force.com Streaming API lets you expose a near real-time stream of data from the Force.com platform. Streaming API delivers events that are either tied to changes in Salesforce or based on custom payloads. Administrators can create topics, to which applications can subscribe, receiving asynchronous notifications via the Bayeux Protocol. Streaming data made simple, secure, and scalable.
Note: For existing apps that poll the SOAP or REST API to detect changes, you should consider refactoring it to use the Streaming API for better performance and lower resource consumption.
This page is the primary resource page for the Streaming API.
To begin learning about the Streaming API, follow this path.
Here are some other helpful resources for the Force.com Streaming API.
Streaming API Developer Guide