Traditionally, applications depending on data from TFS would continuously poll TFS to check for updates. Service Hooks, a new introduction in TFS 2015, provides the means to cascade an event in TFS to another application. When an application registers in TFS for an event notification, a secure queue is created between TFS and the application. When the event the application has registered for happens in TFS, it is published across to the application. This removes the need for applications to poll TFS for updates.
If you aren't familiar with Trello, it is a fantastic web-based tool that helps you set up a Kanban board for pretty much anything. Many organizations use Trello boards for product planning purposes. You can learn more about Trello at https://trello.com.
In this recipe, you'll learn how to create a Service Hook to securely publish a new feature Work Item from Team Portal in TFS to a board in Trello.